The reference manual is the official definition of the Lua language.
+
For a complete introduction to Lua programming, see the book
-Programming in Lua.
+Programming in Lua.
-
-Lua is an extension programming language designed to support
-general procedural programming with data description
-facilities.
-It also offers good support for object-oriented programming,
-functional programming, and data-driven programming.
-Lua is intended to be used as a powerful, lightweight,
-embeddable scripting language for any program that needs one.
+Lua is a powerful, efficient, lightweight, embeddable scripting language.
+It supports procedural programming,
+object-oriented programming, functional programming,
+data-driven programming, and data description.
+
+
+
+Lua combines simple procedural syntax with powerful data description
+constructs based on associative arrays and extensible semantics.
+Lua is dynamically typed,
+runs by interpreting bytecode with a register-based
+virtual machine,
+and has automatic memory management with
+a generational garbage collection,
+making it ideal for configuration, scripting,
+and rapid prototyping.
+
+
+
Lua is implemented as a library, written in clean C,
-the common subset of Standard C and C++.
+the common subset of standard C and C++.
+The Lua distribution includes a host program called lua,
+which uses the Lua library to offer a complete,
+standalone Lua interpreter,
+for interactive or batch use.
+Lua is intended to be used both as a powerful, lightweight,
+embeddable scripting language for any program that needs one,
+and as a powerful but lightweight and efficient stand-alone language.
-Being an extension language, Lua has no notion of a "main" program:
-it only works embedded in a host client,
+As an extension language, Lua has no notion of a "main" program:
+it works embedded in a host client,
called the embedding program or simply the host.
+(Frequently, this host is the stand-alone lua program.)
The host program can invoke functions to execute a piece of Lua code,
can write and read Lua variables,
and can register C functions to be called by Lua code.
Through the use of C functions, Lua can be augmented to cope with
a wide range of different domains,
thus creating customized programming languages sharing a syntactical framework.
-The Lua distribution includes a sample host program called lua,
-which uses the Lua library to offer a complete, standalone Lua interpreter,
-for interactive or batch use.
-Lua is a dynamically typed language.
+Lua is a dynamically typed language.
This means that
variables do not have types; only values do.
There are no type definitions in the language.
@@ -103,7 +126,7 @@
-All values in Lua are first-class values.
+All values in Lua are first-class values.
This means that all values can be stored in variables,
passed as arguments to other functions, and returned as results.
@@ -113,40 +136,78 @@
nil, boolean, number,
string, function, userdata,
thread, and table.
-Nil is the type of the value nil,
+The type nil has one single value, nil,
whose main property is to be different from any other value;
-it usually represents the absence of a useful value.
-Boolean is the type of the values false and true.
+it often represents the absence of a useful value.
+The type boolean has two values, false and true.
Both nil and false make a condition false;
-any other value makes it true.
-Number represents real (double-precision floating-point) numbers.
-Operations on numbers follow the same rules of
-the underlying C implementation,
-which, in turn, usually follows the IEEE 754 standard.
-(It is easy to build Lua interpreters that use other
-internal representations for numbers,
-such as single-precision floats or long integers;
-see file luaconf.h.)
-String represents immutable sequences of bytes.
+they are collectively called false values.
+Any other value makes a condition true.
+Despite its name,
+false is frequently used as an alternative to nil,
+with the key difference that false behaves
+like a regular value in a table,
+while a nil in a table represents an absent key.
+
+
+
+The type number represents both
+integer numbers and real (floating-point) numbers,
+using two subtypes: integer and float.
+Standard Lua uses 64-bit integers and double-precision (64-bit) floats,
+but you can also compile Lua so that it
+uses 32-bit integers and/or single-precision (32-bit) floats.
+The option with 32 bits for both integers and floats
+is particularly attractive
+for small machines and embedded systems.
+(See macro LUA_32BITS in file luaconf.h.)
+
+
+
+Unless stated otherwise,
+any overflow when manipulating integer values wrap around,
+according to the usual rules of two-complement arithmetic.
+(In other words,
+the actual result is the unique representable integer
+that is equal modulo 2n to the mathematical result,
+where n is the number of bits of the integer type.)
+
+
+
+Lua has explicit rules about when each subtype is used,
+but it also converts between them automatically as needed (see §3.4.3).
+Therefore,
+the programmer may choose to mostly ignore the difference
+between integers and floats
+or to assume complete control over the representation of each number.
+
+
+
+The type string represents immutable sequences of bytes.
Lua is 8-bit clean:
strings can contain any 8-bit value,
including embedded zeros ('\0').
+Lua is also encoding-agnostic;
+it makes no assumptions about the contents of a string.
+The length of any string in Lua must fit in a Lua integer.
Lua can call (and manipulate) functions written in Lua and
-functions written in C
-(see §3.4.9).
+functions written in C (see §3.4.10).
+Both are represented by the type function.
The type userdata is provided to allow arbitrary C data to
be stored in Lua variables.
-A userdata value is a pointer to a block of raw memory.
+A userdata value represents a block of raw memory.
There are two kinds of userdata:
-full userdata, where the block of memory is managed by Lua,
-and light userdata, where the block of memory is managed by the host.
+full userdata,
+which is an object with a block of memory managed by Lua,
+and light userdata,
+which is simply a C pointer value.
Userdata has no predefined operations in Lua,
except assignment and identity test.
By using metatables,
@@ -154,46 +215,41 @@
(see §2.4).
Userdata values cannot be created or modified in Lua,
only through the C API.
-This guarantees the integrity of data owned by the host program.
+This guarantees the integrity of data owned by
+the host program and C libraries.
The type thread represents independent threads of execution
and it is used to implement coroutines (see §2.6).
-Do not confuse Lua threads with operating-system threads.
+Lua threads are not related to operating-system threads.
Lua supports coroutines on all systems,
-even those that do not support threads.
+even those that do not support threads natively.
The type table implements associative arrays,
-that is, arrays that can be indexed not only with numbers,
-but with any Lua value except nil and NaN
-(Not a Number, a special numeric value used to represent
-undefined or unrepresentable results, such as 0/0).
+that is, arrays that can have as indices not only numbers,
+but any Lua value except nil and NaN.
+(Not a Number is a special floating-point value
+used by the IEEE 754 standard to represent
+undefined numerical results, such as 0/0.)
Tables can be heterogeneous;
that is, they can contain values of all types (except nil).
-Any key with value nil is not considered part of the table.
+Any key associated to the value nil is not considered part of the table.
Conversely, any key that is not part of a table has
an associated value nil.
-Tables are the sole data structuring mechanism in Lua;
-they can be used to represent ordinary arrays, sequences,
+Tables are the sole data-structuring mechanism in Lua;
+they can be used to represent ordinary arrays, lists,
symbol tables, sets, records, graphs, trees, etc.
To represent records, Lua uses the field name as an index.
The language supports this representation by
providing a.name as syntactic sugar for a["name"].
There are several convenient ways to create tables in Lua
-(see §3.4.8).
-
-
-
-We use the term sequence to denote a table where
-the set of all positive numeric keys is equal to {1..n}
-for some integer n,
-which is called the length of the sequence (see §3.4.6).
+(see §3.4.9).
In particular,
because functions are first-class values,
table fields can contain functions.
-Thus tables can also carry methods (see §3.4.10).
+Thus tables can also carry methods (see §3.4.11).
denote the same table element
if and only if i and j are raw equal
(that is, equal without metamethods).
+In particular, floats with integral values
+are equal to their respective integers
+(e.g., 1.0 == 1).
+To avoid ambiguities,
+any float used as a key that is equal to an integer
+is converted to that integer.
+For instance, if you write a[2.0] = true,
+the actual key inserted into the table will be the integer 2.
-As will be discussed in §3.2 and §3.3.3,
-any reference to a global name var is syntactically translated
-to _ENV.var.
+As we will discuss further in §3.2 and §3.3.3,
+any reference to a free name
+(that is, a name not bound to any declaration) var
+is syntactically translated to _ENV.var.
Moreover, every chunk is compiled in the scope of
-an external local variable called _ENV (see §3.3.2),
-so _ENV itself is never a global name in a chunk.
+an external local variable named _ENV (see §3.3.2),
+so _ENV itself is never a free name in a chunk.
Despite the existence of this external _ENV variable and
-the translation of global names,
+the translation of free names,
_ENV is a completely regular name.
In particular,
you can define new variables and parameters with that name.
-Each reference to a global name uses the _ENV that is
+Each reference to a free name uses the _ENV that is
visible at that point in the program,
following the usual visibility rules of Lua (see §3.5).
@@ -259,81 +324,106 @@
Lua keeps a distinguished environment called the global environment.
-This value is kept at a special index in the C registry (see §4.5).
-In Lua, the variable _G is initialized with this same value.
+This value is kept at a special index in the C registry (see §4.3).
+In Lua, the global variable _G is initialized with this same value.
+(_G is never used internally,
+so changing its value will affect only your own code.)
-When Lua compiles a chunk,
-it initializes the value of its _ENV upvalue
-with the global environment (see load).
+When Lua loads a chunk,
+the default value for its _ENV variable
+is the global environment (see load).
Therefore, by default,
-global variables in Lua code refer to entries in the global environment.
+free names in Lua code refer to entries in the global environment
+and, therefore, they are also called global variables.
Moreover, all standard libraries are loaded in the global environment
-and several functions there operate on that environment.
+and some functions there operate on that environment.
You can use load (or loadfile)
to load a chunk with a different environment.
(In C, you have to load the chunk and then change the value
-of its first upvalue.)
+of its first upvalue; see lua_setupvalue.)
+
+
+
+
-If you change the global environment in the registry
-(through C code or the debug library),
-all chunks loaded after the change will get the new environment.
-Previously loaded chunks are not affected, however,
-as each has its own reference to the environment in its _ENV variable.
-Moreover, the variable _G
-(which is stored in the original global environment)
-is never updated by Lua.
+Several operations in Lua can raise an error.
+An error interrupts the normal flow of the program,
+which can continue by catching the error.
+
+Lua code can explicitly raise an error by calling the
+error function.
+(This function never returns.)
+
+To catch errors in Lua,
+you can do a protected call,
+using pcall (or xpcall).
+The function pcall calls a given function in protected mode.
+Any error while running the function stops its execution,
+and control returns immediately to pcall,
+which returns a status code.
-
Because Lua is an embedded extension language,
-all Lua actions start from C code in the host program
-calling a function from the Lua library (see lua_pcall).
-Whenever an error occurs during
+Lua code starts running by a call
+from C code in the host program.
+(When you use Lua standalone,
+the lua application is the host program.)
+Usually, this call is protected;
+so, when an otherwise unprotected error occurs during
the compilation or execution of a Lua chunk,
control returns to the host,
-which can take appropriate measures
-(such as printing an error message).
-
-
-
-Lua code can explicitly generate an error by calling the
-error function.
-If you need to catch errors in Lua,
-you can use pcall or xpcall
-to call a given function in protected mode.
+which can take appropriate measures,
+such as printing an error message.
Whenever there is an error,
-an error object (also called an error message)
+an error object
is propagated with information about the error.
-Lua itself only generates errors where the error object is a string,
-but programs may generate errors with
-any value for the error object.
+Lua itself only generates errors whose error object is a string,
+but programs can generate errors with
+any value as the error object.
+It is up to the Lua program or its host to handle such error objects.
+For historical reasons,
+an error object is often called an error message,
+even though it does not have to be a string.
-When you use xpcall or lua_pcall,
-you may give a message handler
+When you use xpcall (or lua_pcall, in C)
+you can give a message handler
to be called in case of errors.
-This function is called with the original error message
-and returns a new error message.
+This function is called with the original error object
+and returns a new error object.
It is called before the error unwinds the stack,
so that it can gather more information about the error,
for instance by inspecting the stack and creating a stack traceback.
This message handler is still protected by the protected call;
so, an error inside the message handler
will call the message handler again.
-If this loop goes on, Lua breaks it and returns an appropriate message.
+If this loop goes on for too long,
+Lua breaks it and returns an appropriate message.
+The message handler is called only for regular runtime errors.
+It is not called for memory-allocation errors
+nor for errors while running finalizers or other message handlers.
+
+
+
+Lua also offers a system of warnings (see warn).
+Unlike errors, warnings do not interfere
+in any way with program execution.
+They typically only generate a message to the user,
+although this behavior can be adapted from C (see lua_setwarnf).
@@ -345,38 +435,44 @@
Every value in Lua can have a metatable.
This metatable is an ordinary Lua table
that defines the behavior of the original value
-under certain special operations.
+under certain events.
You can change several aspects of the behavior
-of operations over a value by setting specific fields in its metatable.
+of a value by setting specific fields in its metatable.
For instance, when a non-numeric value is the operand of an addition,
-Lua checks for a function in the field "__add" of the value's metatable.
+Lua checks for a function in the field __add of the value's metatable.
If it finds one,
Lua calls this function to perform the addition.
-The keys in a metatable are derived from the event names;
-the corresponding values are called metamethods.
-In the previous example, the event is "add"
+The key for each event in a metatable is a string
+with the event name prefixed by two underscores;
+the corresponding value is called a metavalue.
+For most events, the metavalue must be a function,
+which is then called a metamethod.
+In the previous example, the key is the string "__add"
and the metamethod is the function that performs the addition.
+Unless stated otherwise,
+a metamethod can in fact be any callable value,
+which is either a function or a value with a __call metamethod.
You can query the metatable of any value
using the getmetatable function.
+Lua queries metamethods in metatables using a raw access (see rawget).
You can replace the metatable of tables
using the setmetatable function.
-You cannot change the metatable of other types from Lua
-(except by using the debug library);
-you must use the C API for that.
+You cannot change the metatable of other types from Lua code,
+except by using the debug library (§6.10).
-Tables and full userdata have individual metatables
-(although multiple tables and userdata can share their metatables).
+Tables and full userdata have individual metatables,
+although multiple tables and userdata can share their metatables.
Values of all other types share one single metatable per type;
that is, there is one single metatable for all numbers,
one for all strings, etc.
@@ -385,477 +481,424 @@
-A metatable controls how an object behaves in arithmetic operations,
-order comparisons, concatenation, length operation, and indexing.
-A metatable also can define a function to be called
-when a userdata or a table is garbage collected.
-When Lua performs one of these operations over a value,
-it checks whether this value has a metatable with the corresponding event.
-If so, the value associated with that key (the metamethod)
-controls how Lua will perform the operation.
-
-
-
-Metatables control the operations listed next.
-Each operation is identified by its corresponding name.
-The key for each operation is a string with its name prefixed by
-two underscores, '__';
-for instance, the key for operation "add" is the
-string "__add".
-
-
-
-The semantics of these operations is better explained by a Lua function
-describing how the interpreter executes the operation.
-The code shown here in Lua is only illustrative;
-the real behavior is hard coded in the interpreter
-and it is much more efficient than this simulation.
-All functions used in these descriptions
-(rawget, tonumber, etc.)
-are described in §6.1.
-In particular, to retrieve the metamethod of a given object,
-we use the expression
-
-
- metatable(obj)[event]
-
-This should be read as
-
-
- rawget(getmetatable(obj) or {}, event)
-
-
-This means that the access to a metamethod does not invoke other metamethods,
-and access to objects with no metatables does not fail
-(it simply results in nil).
-
-
-
-For the unary - and # operators,
-the metamethod is called with a dummy second argument.
-This extra argument is only to simplify Lua's internals;
-it may be removed in future versions and therefore it is not present
-in the following code.
-(For most uses this extra argument is irrelevant.)
+A detailed list of operations controlled by metatables is given next.
+Each event is identified by its corresponding key.
+By convention, all metatable keys used by Lua are composed by
+two underscores followed by lowercase Latin letters.
-
"add":
-the + operation.
-
-
-
-
-The function getbinhandler below defines how Lua chooses a handler
-for a binary operation.
-First, Lua tries the first operand.
-If its type does not define a handler for the operation,
-then Lua tries the second operand.
-
-
- function getbinhandler (op1, op2, event)
- return metatable(op1)[event] or metatable(op2)[event]
- end
-
-By using this function,
-the behavior of the op1 + op2 is
-
-
- function add_event (op1, op2)
- local o1, o2 = tonumber(op1), tonumber(op2)
- if o1 and o2 then -- both operands are numeric?
- return o1 + o2 -- '+' here is the primitive 'add'
- else -- at least one of the operands is not numeric
- local h = getbinhandler(op1, op2, "__add")
- if h then
- -- call the handler with both operands
- return (h(op1, op2))
- else -- no handler available: default behavior
- error(···)
- end
- end
- end
-
+
__add:
+the addition (+) operation.
+If any operand for an addition is not a number,
+Lua will try to call a metamethod.
+It starts by checking the first operand (even if it is a number);
+if that operand does not define a metamethod for __add,
+then Lua will check the second operand.
+If Lua can find a metamethod,
+it calls the metamethod with the two operands as arguments,
+and the result of the call
+(adjusted to one value)
+is the result of the operation.
+Otherwise, if no metamethod is found,
+Lua raises an error.
-
"sub":
-the - operation.
-
-Behavior similar to the "add" operation.
+
__sub:
+the subtraction (-) operation.
+Behavior similar to the addition operation.
-
"mul":
-the * operation.
-
-Behavior similar to the "add" operation.
+
__mul:
+the multiplication (*) operation.
+Behavior similar to the addition operation.
-
"div":
-the / operation.
-
-Behavior similar to the "add" operation.
+
__div:
+the division (/) operation.
+Behavior similar to the addition operation.
-
"mod":
-the % operation.
-
-Behavior similar to the "add" operation,
-with the operation
-o1 - floor(o1/o2)*o2 as the primitive operation.
+
__mod:
+the modulo (%) operation.
+Behavior similar to the addition operation.
-
"pow":
-the ^ (exponentiation) operation.
-
-Behavior similar to the "add" operation,
-with the function pow (from the C math library)
-as the primitive operation.
+
__pow:
+the exponentiation (^) operation.
+Behavior similar to the addition operation.
-
"unm":
-the unary - operation.
+
__unm:
+the negation (unary -) operation.
+Behavior similar to the addition operation.
+
+
__idiv:
+the floor division (//) operation.
+Behavior similar to the addition operation.
+
-
- function unm_event (op)
- local o = tonumber(op)
- if o then -- operand is numeric?
- return -o -- '-' here is the primitive 'unm'
- else -- the operand is not numeric.
- -- Try to get a handler from the operand
- local h = metatable(op).__unm
- if h then
- -- call the handler with the operand
- return (h(op))
- else -- no handler available: default behavior
- error(···)
- end
- end
- end
-
+
__band:
+the bitwise AND (&) operation.
+Behavior similar to the addition operation,
+except that Lua will try a metamethod
+if any operand is neither an integer
+nor a float coercible to an integer (see §3.4.3).
-
"concat":
-the .. (concatenation) operation.
+
__bor:
+the bitwise OR (|) operation.
+Behavior similar to the bitwise AND operation.
+
+
__bxor:
+the bitwise exclusive OR (binary ~) operation.
+Behavior similar to the bitwise AND operation.
+
-
- function concat_event (op1, op2)
- if (type(op1) == "string" or type(op1) == "number") and
- (type(op2) == "string" or type(op2) == "number") then
- return op1 .. op2 -- primitive string concatenation
- else
- local h = getbinhandler(op1, op2, "__concat")
- if h then
- return (h(op1, op2))
- else
- error(···)
- end
- end
- end
-
+
__bnot:
+the bitwise NOT (unary ~) operation.
+Behavior similar to the bitwise AND operation.
-
"len":
-the # operation.
+
__shl:
+the bitwise left shift (<<) operation.
+Behavior similar to the bitwise AND operation.
+
+
__shr:
+the bitwise right shift (>>) operation.
+Behavior similar to the bitwise AND operation.
+
-
- function len_event (op)
- if type(op) == "string" then
- return strlen(op) -- primitive string length
- else
- local h = metatable(op).__len
- if h then
- return (h(op)) -- call handler with the operand
- elseif type(op) == "table" then
- return #op -- primitive table length
- else -- no handler available: error
- error(···)
- end
- end
- end
-
-See §3.4.6 for a description of the length of a table.
+
__concat:
+the concatenation (..) operation.
+Behavior similar to the addition operation,
+except that Lua will try a metamethod
+if any operand is neither a string nor a number
+(which is always coercible to a string).
-
"eq":
-the == operation.
+
__len:
+the length (#) operation.
+If the object is not a string,
+Lua will try its metamethod.
+If there is a metamethod,
+Lua calls it with the object as argument,
+and the result of the call
+(always adjusted to one value)
+is the result of the operation.
+If there is no metamethod but the object is a table,
+then Lua uses the table length operation (see §3.4.7).
+Otherwise, Lua raises an error.
+
-The function getequalhandler defines how Lua chooses a metamethod
-for equality.
-A metamethod is selected only when both values
-being compared have the same type
-and the same metamethod for the selected operation,
-and the values are either tables or full userdata.
+
__eq:
+the equal (==) operation.
+Behavior similar to the addition operation,
+except that Lua will try a metamethod only when the values
+being compared are either both tables or both full userdata
+and they are not primitively equal.
+The result of the call is always converted to a boolean.
+
-
- function getequalhandler (op1, op2)
- if type(op1) ~= type(op2) or
- (type(op1) ~= "table" and type(op1) ~= "userdata") then
- return nil -- different values
- end
- local mm1 = metatable(op1).__eq
- local mm2 = metatable(op2).__eq
- if mm1 == mm2 then return mm1 else return nil end
- end
-
-The "eq" event is defined as follows:
+
__lt:
+the less than (<) operation.
+Behavior similar to the addition operation,
+except that Lua will try a metamethod only when the values
+being compared are neither both numbers nor both strings.
+Moreover, the result of the call is always converted to a boolean.
+
-
- function eq_event (op1, op2)
- if op1 == op2 then -- primitive equal?
- return true -- values are equal
- end
- -- try metamethod
- local h = getequalhandler(op1, op2)
- if h then
- return not not h(op1, op2)
- else
- return false
- end
- end
-
-Note that the result is always a boolean.
+
__le:
+the less equal (<=) operation.
+Behavior similar to the less than operation.
-
"lt":
-the < operation.
+
__index:
+The indexing access operation table[key].
+This event happens when table is not a table or
+when key is not present in table.
+The metavalue is looked up in the metatable of table.
-
- function lt_event (op1, op2)
- if type(op1) == "number" and type(op2) == "number" then
- return op1 < op2 -- numeric comparison
- elseif type(op1) == "string" and type(op2) == "string" then
- return op1 < op2 -- lexicographic comparison
- else
- local h = getbinhandler(op1, op2, "__lt")
- if h then
- return not not h(op1, op2)
- else
- error(···)
- end
- end
- end
-
-Note that the result is always a boolean.
+
+The metavalue for this event can be either a function, a table,
+or any value with an __index metavalue.
+If it is a function,
+it is called with table and key as arguments,
+and the result of the call
+(adjusted to one value)
+is the result of the operation.
+Otherwise,
+the final result is the result of indexing this metavalue with key.
+This indexing is regular, not raw,
+and therefore can trigger another __index metavalue.
-
"le":
-the <= operation.
+
__newindex:
+The indexing assignment table[key] = value.
+Like the index event,
+this event happens when table is not a table or
+when key is not present in table.
+The metavalue is looked up in the metatable of table.
-
- function le_event (op1, op2)
- if type(op1) == "number" and type(op2) == "number" then
- return op1 <= op2 -- numeric comparison
- elseif type(op1) == "string" and type(op2) == "string" then
- return op1 <= op2 -- lexicographic comparison
- else
- local h = getbinhandler(op1, op2, "__le")
- if h then
- return not not h(op1, op2)
- else
- h = getbinhandler(op1, op2, "__lt")
- if h then
- return not h(op2, op1)
- else
- error(···)
- end
- end
- end
- end
-
-Note that, in the absence of a "le" metamethod,
-Lua tries the "lt", assuming that a <= b is
-equivalent to not (b < a).
+
+Like with indexing,
+the metavalue for this event can be either a function, a table,
+or any value with an __newindex metavalue.
+If it is a function,
+it is called with table, key, and value as arguments.
+Otherwise,
+Lua repeats the indexing assignment over this metavalue
+with the same key and value.
+This assignment is regular, not raw,
+and therefore can trigger another __newindex metavalue.
-As with the other comparison operators,
-the result is always a boolean.
+Whenever a __newindex metavalue is invoked,
+Lua does not perform the primitive assignment.
+If needed,
+the metamethod itself can call rawset
+to do the assignment.
-
"index":
-The indexing access table[key].
-Note that the metamethod is tried only
-when key is not present in table.
-(When table is not a table,
-no key is ever present,
-so the metamethod is always tried.)
+
__call:
+The call operation func(args).
+This event happens when Lua tries to call a non-function value
+(that is, func is not a function).
+The metamethod is looked up in func.
+If present,
+the metamethod is called with func as its first argument,
+followed by the arguments of the original call (args).
+All results of the call
+are the results of the operation.
+This is the only metamethod that allows multiple results.
+
+
-
- function gettable_event (table, key)
- local h
- if type(table) == "table" then
- local v = rawget(table, key)
- -- if key is present, return raw value
- if v ~= nil then return v end
- h = metatable(table).__index
- if h == nil then return nil end
- else
- h = metatable(table).__index
- if h == nil then
- error(···)
- end
- end
- if type(h) == "function" then
- return (h(table, key)) -- call the handler
- else return h[key] -- or repeat operation on it
- end
- end
-
-
+
+In addition to the previous list,
+the interpreter also respects the following keys in metatables:
+__gc (see §2.5.3),
+__close (see §3.3.8),
+__mode (see §2.5.4),
+and __name.
+(The entry __name,
+when it contains a string,
+may be used by tostring and in error messages.)
-
"newindex":
-The indexing assignment table[key] = value.
-Note that the metamethod is tried only
-when key is not present in table.
+
+For the unary operators (negation, length, and bitwise NOT),
+the metamethod is computed and called with a dummy second operand,
+equal to the first one.
+This extra operand is only to simplify Lua's internals
+(by making these operators behave like a binary operation)
+and may be removed in future versions.
+For most uses this extra operand is irrelevant.
-
- function settable_event (table, key, value)
- local h
- if type(table) == "table" then
- local v = rawget(table, key)
- -- if key is present, do raw assignment
- if v ~= nil then rawset(table, key, value); return end
- h = metatable(table).__newindex
- if h == nil then rawset(table, key, value); return end
- else
- h = metatable(table).__newindex
- if h == nil then
- error(···)
- end
- end
- if type(h) == "function" then
- h(table, key,value) -- call the handler
- else h[key] = value -- or repeat operation on it
- end
- end
-
-
-
"call":
-called when Lua calls a value.
+
+Because metatables are regular tables,
+they can contain arbitrary fields,
+not only the event names defined above.
+Some functions in the standard library
+(e.g., tostring)
+use other fields in metatables for their own purposes.
-
- function function_event (func, ...)
- if type(func) == "function" then
- return func(...) -- primitive call
- else
- local h = metatable(func).__call
- if h then
- return h(func, ...)
- else
- error(···)
- end
- end
- end
-
-
+
+It is a good practice to add all needed metamethods to a table
+before setting it as a metatable of some object.
+In particular, the __gc metamethod works only when this order
+is followed (see §2.5.3).
+It is also a good practice to set the metatable of an object
+right after its creation.
-
Lua performs automatic memory management.
This means that
-you have to worry neither about allocating memory for new objects
-nor about freeing it when the objects are no longer needed.
+you do not have to worry about allocating memory for new objects
+or freeing it when the objects are no longer needed.
Lua manages memory automatically by running
-a garbage collector to collect all dead objects
-(that is, objects that are no longer accessible from Lua).
+a garbage collector to collect all dead objects.
All memory used by Lua is subject to automatic management:
strings, tables, userdata, functions, threads, internal structures, etc.
-Lua implements an incremental mark-and-sweep collector.
-It uses two numbers to control its garbage-collection cycles:
-the garbage-collector pause and
-the garbage-collector step multiplier.
-Both use percentage points as units
-(e.g., a value of 100 means an internal value of 1).
+An object is considered dead
+as soon as the collector can be sure the object
+will not be accessed again in the normal execution of the program.
+("Normal execution" here excludes finalizers,
+which can resurrect dead objects (see §2.5.3),
+and excludes also operations using the debug library.)
+Note that the time when the collector can be sure that an object
+is dead may not coincide with the programmer's expectations.
+The only guarantees are that Lua will not collect an object
+that may still be accessed in the normal execution of the program,
+and it will eventually collect an object
+that is inaccessible from Lua.
+(Here,
+inaccessible from Lua means that neither a variable nor
+another live object refer to the object.)
+Because Lua has no knowledge about C code,
+it never collects objects accessible through the registry (see §4.3),
+which includes the global environment (see §2.2).
+
+
+
+The garbage collector (GC) in Lua can work in two modes:
+incremental and generational.
+
+
+
+The default GC mode with the default parameters
+are adequate for most uses.
+However, programs that waste a large proportion of their time
+allocating and freeing memory can benefit from other settings.
+Keep in mind that the GC behavior is non-portable
+both across platforms and across different Lua releases;
+therefore, optimal settings are also non-portable.
+
+
+
+You can change the GC mode and parameters by calling
+lua_gc in C
+or collectgarbage in Lua.
+You can also use these functions to control
+the collector directly (e.g., to stop and restart it).
+
+
+
+
+
+
+In incremental mode,
+each GC cycle performs a mark-and-sweep collection in small steps
+interleaved with the program's execution.
+In this mode,
+the collector uses three numbers to control its garbage-collection cycles:
+the garbage-collector pause,
+the garbage-collector step multiplier,
+and the garbage-collector step size.
The garbage-collector pause
controls how long the collector waits before starting a new cycle.
+The collector starts a new cycle when the use of memory
+hits n% of the use after the previous collection.
Larger values make the collector less aggressive.
-Values smaller than 100 mean the collector will not wait to
+Values equal to or less than 100 mean the collector will not wait to
start a new cycle.
A value of 200 means that the collector waits for the total memory in use
to double before starting a new cycle.
+The default value is 200; the maximum value is 1000.
The garbage-collector step multiplier
-controls the relative speed of the collector relative to
-memory allocation.
+controls the speed of the collector relative to
+memory allocation,
+that is,
+how many elements it marks or sweeps for each
+kilobyte of memory allocated.
Larger values make the collector more aggressive but also increase
the size of each incremental step.
-Values smaller than 100 make the collector too slow and
+You should not use values less than 100,
+because they make the collector too slow and
can result in the collector never finishing a cycle.
-The default is 200,
-which means that the collector runs at "twice"
-the speed of memory allocation.
+The default value is 100; the maximum value is 1000.
-If you set the step multiplier to a very large number
-(larger than 10% of the maximum number of
-bytes that the program may use),
-the collector behaves like a stop-the-world collector.
-If you then set the pause to 200,
-the collector behaves as in old Lua versions,
-doing a complete collection every time Lua doubles its
-memory usage.
+The garbage-collector step size controls the
+size of each incremental step,
+specifically how many bytes the interpreter allocates
+before performing a step.
+This parameter is logarithmic:
+A value of n means the interpreter will allocate 2n
+bytes between steps and perform equivalent work during the step.
+A large value (e.g., 60) makes the collector a stop-the-world
+(non-incremental) collector.
+The default value is 13,
+which means steps of approximately 8 Kbytes.
+
+
+
+
-You can change these numbers by calling lua_gc in C
-or collectgarbage in Lua.
-You can also use these functions to control
-the collector directly (e.g., stop and restart it).
+In generational mode,
+the collector does frequent minor collections,
+which traverses only objects recently created.
+If after a minor collection the use of memory is still above a limit,
+the collector does a stop-the-world major collection,
+which traverses all objects.
+The generational mode uses two parameters:
+the minor multiplier and the the major multiplier.
+
+
+
+The minor multiplier controls the frequency of minor collections.
+For a minor multiplier x,
+a new minor collection will be done when memory
+grows x% larger than the memory in use after the previous major
+collection.
+For instance, for a multiplier of 20,
+the collector will do a minor collection when the use of memory
+gets 20% larger than the use after the previous major collection.
+The default value is 20; the maximum value is 200.
-As an experimental feature in Lua 5.2,
-you can change the collector's operation mode
-from incremental to generational.
-A generational collector assumes that most objects die young,
-and therefore it traverses only young (recently created) objects.
-This behavior can reduce the time used by the collector,
-but also increases memory usage (as old dead objects may accumulate).
-To mitigate this second problem,
-from time to time the generational collector performs a full collection.
-Remember that this is an experimental feature;
-you are welcome to try it,
-but check your gains.
+The major multiplier controls the frequency of major collections.
+For a major multiplier x,
+a new major collection will be done when memory
+grows x% larger than the memory in use after the previous major
+collection.
+For instance, for a multiplier of 100,
+the collector will do a major collection when the use of memory
+gets larger than twice the use after the previous collection.
+The default value is 100; the maximum value is 1000.
+
-
You can set garbage-collector metamethods for tables
and, using the C API,
for full userdata (see §2.4).
-These metamethods are also called finalizers.
+These metamethods, called finalizers,
+are called when the garbage collector detects that the
+corresponding table or userdata is dead.
Finalizers allow you to coordinate Lua's garbage collection
-with external resource management
-(such as closing files, network or database connections,
-or freeing your own memory).
+with external resource management such as closing files,
+network or database connections,
+or freeing your own memory.
you must mark it for finalization.
You mark an object for finalization when you set its metatable
-and the metatable has a field indexed by the string "__gc".
+and the metatable has a __gc metamethod.
Note that if you set a metatable without a __gc field
and later create that field in the metatable,
the object will not be marked for finalization.
-However, after an object is marked,
-you can freely change the __gc field of its metatable.
-When a marked object becomes garbage,
+When a marked object becomes dead,
it is not collected immediately by the garbage collector.
Instead, Lua puts it in a list.
After the collection,
-Lua does the equivalent of the following function
-for each object in that list:
+Lua goes through that list.
+For each object in the list,
+it checks the object's __gc metamethod:
+If it is present,
+Lua calls it with the object as its single argument.
-
- function gc_event (obj)
- local h = metatable(obj).__gc
- if type(h) == "function" then
- h(obj)
- end
- end
-
At the end of each garbage-collection cycle,
-the finalizers for objects are called in
-the reverse order that they were marked for collection,
+the finalizers are called in
+the reverse order that the objects were marked for finalization,
among those collected in that cycle;
that is, the first finalizer to be called is the one associated
with the object marked last in the program.
@@ -901,30 +937,46 @@
Because the object being collected must still be used by the finalizer,
-it (and other objects accessible only through it)
+that object (and other objects accessible only through it)
must be resurrected by Lua.
Usually, this resurrection is transient,
and the object memory is freed in the next garbage-collection cycle.
However, if the finalizer stores the object in some global place
(e.g., a global variable),
-then there is a permanent resurrection.
+then the resurrection is permanent.
+Moreover, if the finalizer marks a finalizing object for finalization again,
+its finalizer will be called again in the next cycle where the
+object is dead.
In any case,
-the object memory is freed only when it becomes completely inaccessible;
-its finalizer will never be called twice.
+the object memory is freed only in a GC cycle where
+the object is dead and not marked for finalization.
When you close a state (see lua_close),
-Lua calls the finalizers of all objects marked for collection,
+Lua calls the finalizers of all objects marked for finalization,
following the reverse order that they were marked.
-If any finalizer marks new objects for collection during that phase,
-these new objects will not be finalized.
+If any finalizer marks objects for collection during that phase,
+these marks have no effect.
+
+Finalizers cannot yield nor run the garbage collector.
+Because they can run in unpredictable times,
+it is good practice to restrict each finalizer
+to the minimum necessary to properly release
+its associated resource.
+
+
+
+Any error while running a finalizer generates a warning;
+the error is not propagated.
+
-
A weak table can have weak keys, weak values, or both.
-A table with weak keys allows the collection of its keys,
-but prevents the collection of its values.
+A table with weak values allows the collection of its values,
+but prevents the collection of its keys.
A table with both weak keys and weak values allows the collection of
both keys and values.
In any case, if either the key or the value is collected,
the whole pair is removed from the table.
The weakness of a table is controlled by the
__mode field of its metatable.
-If the __mode field is a string containing the character 'k',
-the keys in the table are weak.
-If __mode contains 'v',
-the values in the table are weak.
+This metavalue, if present, must be one of the following strings:
+"k", for a table with weak keys;
+"v", for a table with weak values;
+or "kv", for a table with both weak keys and values.
Only objects that have an explicit construction
are removed from weak tables.
-Values, such as numbers and light C functions,
+Values, such as numbers and light C functions,
are not subject to garbage collection,
and therefore are not removed from weak tables
-(unless its associated value is collected).
+(unless their associated values are collected).
Although strings are subject to garbage collection,
-they do not have an explicit construction,
-and therefore are not removed from weak tables.
+they do not have an explicit construction and
+their equality is by value;
+they behave more like values than like objects.
+Therefore, they are not removed from weak tables.
When you first call coroutine.resume,
passing as its first argument
a thread returned by coroutine.create,
-the coroutine starts its execution,
-at the first line of its main function.
-Extra arguments passed to coroutine.resume are passed on
-to the coroutine main function.
+the coroutine starts its execution by
+calling its main function.
+Extra arguments passed to coroutine.resume are passed
+as arguments to that function.
After the coroutine starts running,
it runs until it terminates or yields.
@@ -1041,10 +1095,14 @@
normally, when its main function returns
(explicitly or implicitly, after the last instruction);
and abnormally, if there is an unprotected error.
-In the first case, coroutine.resume returns true,
+In case of normal termination,
+coroutine.resume returns true,
plus any values returned by the coroutine main function.
In case of errors, coroutine.resume returns false
-plus an error message.
+plus the error object.
+In this case, the coroutine does not unwind its stack,
+so that it is possible to inspect it after the error
+with the debug API.
coroutine.wrap returns all the values returned by coroutine.resume,
except the first one (the boolean error code).
Unlike coroutine.resume,
-coroutine.wrap does not catch errors;
-any error is propagated to the caller.
+the function created by coroutine.wrap
+propagates any error to the caller.
+In this case,
+the function also closes the coroutine (see coroutine.close).
Lua is a free-form language.
-It ignores spaces (including new lines) and comments
-between lexical elements (tokens),
-except as delimiters between names and keywords.
+It ignores spaces and comments between lexical elements (tokens),
+except as delimiters between two tokens.
+In source code,
+Lua recognizes as spaces the standard ASCII whitespace
+characters space, form feed, newline,
+carriage return, horizontal tab, and vertical tab.
Names
(also called identifiers)
-in Lua can be any string of letters,
-digits, and underscores,
-not beginning with a digit.
+in Lua can be any string of Latin letters,
+Arabic-Indic digits, and underscores,
+not beginning with a digit and
+not being a reserved word.
Identifiers are used to name variables, table fields, and labels.
@@ -1180,9 +1248,10 @@
Lua is a case-sensitive language:
and is a reserved word, but And and AND
are two different, valid names.
-As a convention, names starting with an underscore followed by
-uppercase letters (such as _VERSION)
-are reserved for variables used by Lua.
+As a convention,
+programs should avoid creating
+names that start with an underscore followed by
+one or more uppercase letters (such as _VERSION).
-Literal strings
+A short literal string
can be delimited by matching single or double quotes,
and can contain the following C-like escape sequences:
'\a' (bell),
@@ -1209,26 +1279,41 @@
'\\' (backslash),
'\"' (quotation mark [double quote]),
and '\'' (apostrophe [single quote]).
-A backslash followed by a real newline
+A backslash followed by a line break
results in a newline in the string.
The escape sequence '\z' skips the following span
-of white-space characters,
+of whitespace characters,
including line breaks;
it is particularly useful to break and indent a long literal string
into multiple lines without adding the newlines and spaces
into the string contents.
+A short literal string cannot contain unescaped line breaks
+nor escapes not forming a valid escape sequence.
-A byte in a literal string can also be specified by its numerical value.
-This can be done with the escape sequence \xXX,
+We can specify any byte in a short literal string,
+including embedded zeros,
+by its numeric value.
+This can be done
+with the escape sequence \xXX,
where XX is a sequence of exactly two hexadecimal digits,
or with the escape sequence \ddd,
where ddd is a sequence of up to three decimal digits.
-(Note that if a decimal escape is to be followed by a digit,
+(Note that if a decimal escape sequence is to be followed by a digit,
it must be expressed using exactly three digits.)
-Strings in Lua can contain any 8-bit value, including embedded zeros,
-which can be specified as '\0'.
+
+
+
+The UTF-8 encoding of a Unicode character
+can be inserted in a literal string with
+the escape sequence \u{XXX}
+(with mandatory enclosing braces),
+where XXX is a sequence of one or more hexadecimal digits
+representing the character code point.
+This code point can be any value less than 231.
+(Lua uses the original UTF-8 specification here,
+which is not restricted to valid Unicode code points.)
We define an opening long bracket of level n as an opening
square bracket followed by n equal signs followed by another
opening square bracket.
-So, an opening long bracket of level 0 is written as [[,
-an opening long bracket of level 1 is written as [=[,
+So, an opening long bracket of level 0 is written as [[,
+an opening long bracket of level 1 is written as [=[,
and so on.
A closing long bracket is defined similarly;
-for instance, a closing long bracket of level 4 is written as ]====].
+for instance,
+a closing long bracket of level 4 is written as ]====].
A long literal starts with an opening long bracket of any level and
ends at the first closing long bracket of the same level.
-It can contain any text except a closing bracket of the proper level.
+It can contain any text except a closing bracket of the same level.
Literals in this bracketed form can run for several lines,
do not interpret any escape sequences,
and ignore long brackets of any other level.
@@ -1252,24 +1338,11 @@
(carriage return, newline, carriage return followed by newline,
or newline followed by carriage return)
is converted to a simple newline.
+When the opening long bracket is immediately followed by a newline,
+the newline is not included in the string.
-When parsing a from a string source,
-any byte in a literal string not
-explicitly affected by the previous rules represents itself.
-However, Lua opens files for parsing in text mode,
-and the system file functions may have problems with
-some control characters.
-So, it is safer to represent
-non-text data as a quoted literal with
-explicit escape sequences for non-text characters.
-
-
-
-For convenience,
-when the opening long bracket is immediately followed by a newline,
-the newline is not included in the string.
As an example, in a system using ASCII
(in which 'a' is coded as 97,
newline is coded as 10, and '1' is coded as 49),
@@ -1287,19 +1360,55 @@
-A numerical constant can be written with an optional fractional part
+Any byte in a literal string not
+explicitly affected by the previous rules represents itself.
+However, Lua opens files for parsing in text mode,
+and the system's file functions may have problems with
+some control characters.
+So, it is safer to represent
+binary data as a quoted literal with
+explicit escape sequences for the non-text characters.
+
+
+
+A numeric constant (or numeral)
+can be written with an optional fractional part
and an optional decimal exponent,
marked by a letter 'e' or 'E'.
Lua also accepts hexadecimal constants,
which start with 0x or 0X.
Hexadecimal constants also accept an optional fractional part
plus an optional binary exponent,
-marked by a letter 'p' or 'P'.
-Examples of valid numerical constants are
+marked by a letter 'p' or 'P' and written in decimal.
+(For instance, 0x1.fp10 denotes 1984,
+which is 0x1f / 16 multiplied by 210.)
+
+
+
+A numeric constant with a radix point or an exponent
+denotes a float;
+otherwise,
+if its value fits in an integer or it is a hexadecimal constant,
+it denotes an integer;
+otherwise (that is, a decimal integer numeral that overflows),
+it denotes a float.
+Hexadecimal numerals with neither a radix point nor an exponent
+always denote an integer value;
+if the value overflows, it wraps around
+to fit into a valid integer.
+
+
+
which runs until the end of the line.
Otherwise, it is a long comment,
which runs until the corresponding closing long bracket.
-Long comments are frequently used to disable code temporarily.
@@ -1332,7 +1440,7 @@
-The meaning of accesses to table fields can be changed via metatables.
-An access to an indexed variable t[i] is equivalent to
-a call gettable_event(t,i).
-(See §2.4 for a complete description of the
-gettable_event function.
-This function is not defined or callable in Lua.
-We use it here only for explanatory purposes.)
+The meaning of accesses to table fields can be changed via metatables
+(see §2.4).
An access to a global variable x
is equivalent to _ENV.x.
Due to the way that chunks are compiled,
-_ENV is never a global name (see §2.2).
+the variable _ENV itself is never global (see §2.2).
@@ -1382,15 +1485,19 @@
Lua supports an almost conventional set of statements,
-similar to those in Pascal or C.
+similar to those in other conventional languages.
This set includes
-assignments, control structures, function calls,
+blocks, assignments, control structures, function calls,
and variable declarations.
+
+
+Both function calls and assignments
+can start with an open parenthesis.
+This possibility leads to an ambiguity in Lua's grammar.
+Consider the following fragment:
+
+
+ a = b + c
+ (print or io.write)('done')
+
+The grammar could see this fragment in two ways:
+
+
+ a = b + c(print or io.write)('done')
+
+ a = b + c; (print or io.write)('done')
+
+The current parser always sees such constructions
+in the first way,
+interpreting the open parenthesis
+as the start of the arguments to a call.
+To avoid this ambiguity,
+it is a good practice to always precede with a semicolon
+statements that start with a parenthesis:
+
+
+ ;(print or io.write)('done')
+
+
A block can be explicitly delimited to produce a single statement:
@@ -1428,7 +1564,7 @@
-The unit of execution of Lua is called a chunk.
+The unit of compilation of Lua is called a chunk.
Syntactically,
a chunk is simply a block:
@@ -1439,29 +1575,29 @@
Lua handles a chunk as the body of an anonymous function
with a variable number of arguments
-(see §3.4.10).
+(see §3.4.11).
As such, chunks can define local variables,
receive arguments, and return values.
Moreover, such anonymous function is compiled as in the
scope of an external local variable called _ENV (see §2.2).
-The resulting function always has _ENV as its only upvalue,
+The resulting function always has _ENV as its only external variable,
even if it does not use that variable.
A chunk can be stored in a file or in a string inside the host program.
To execute a chunk,
-Lua first precompiles the chunk into instructions for a virtual machine,
-and then it executes the compiled code
+Lua first loads it,
+precompiling the chunk's code into instructions for a virtual machine,
+and then Lua executes the compiled code
with an interpreter for the virtual machine.
Chunks can also be precompiled into binary form;
-see program luac for details.
+see the program luac and the function string.dump for details.
Programs in source and compiled forms are interchangeable;
-Lua automatically detects the file type and acts accordingly.
-
+Lua automatically detects the file type and acts accordingly (see load).
@@ -1487,20 +1623,14 @@
Before the assignment,
the list of values is adjusted to the length of
-the list of variables.
-If there are more values than needed,
-the excess values are thrown away.
-If there are fewer values than needed,
-the list is extended with as many nil's as needed.
-If the list of expressions ends with a function call,
-then all values returned by that call enter the list of values,
-before the adjustment
-(except when the call is enclosed in parentheses; see §3.4).
+the list of variables (see §3.4.12).
-The assignment statement first evaluates all its expressions
-and only then are the assignments performed.
+If a variable is both assigned and read
+inside a multiple assignment,
+Lua ensures that all reads get the value of the variable
+before the assignment.
Thus the code
-The meaning of assignments to global variables
-and table fields can be changed via metatables.
-An assignment to an indexed variable t[i] = val is equivalent to
-settable_event(t,i,val).
-(See §2.4 for a complete description of the
-settable_event function.
-This function is not defined or callable in Lua.
-We use it here only for explanatory purposes.)
+Note that this guarantee covers only accesses
+syntactically inside the assignment statement.
+If a function or a metamethod called during the assignment
+changes the value of a variable,
+Lua gives no guarantees about the order of that access.
-An assignment to a global variable x = val
+An assignment to a global name x = val
is equivalent to the assignment
_ENV.x = val (see §2.2).
+
+The meaning of assignments to table fields and
+global variables (which are actually table fields, too)
+can be changed via metatables (see §2.4).
+
+
@@ -1563,9 +1696,9 @@
The condition expression of a
control structure can return any value.
-Both false and nil are considered false.
-All values different from nil and false are considered true
-(in particular, the number 0 and the empty string are also true).
+Both false and nil test false.
+All values different from nil and false test true.
+In particular, the number 0 and the empty string also test true.
A label is visible in the entire block where it is defined,
-except
-inside nested blocks where a label with the same name is defined and
-inside nested functions.
-A goto may jump to any visible label as long as it does not
+except inside nested functions.
+A goto can jump to any visible label as long as it does not
enter into the scope of a local variable.
-
-
-
-Labels and empty statements are called void statements,
-as they perform no actions.
+A label should not be declared
+where a label with the same name is visible,
+even if this other label has been declared in an enclosing block.
The return statement is used to return values
-from a function or a chunk (which is a function in disguise).
+from a function or a chunk
+(which is handled as an anonymous function).
Functions can return more than one value,
so the syntax for the return statement is
@@ -1629,7 +1759,7 @@
The return statement can only be written
as the last statement of a block.
-If it is really necessary to return in the middle of a block,
+If it is necessary to return in the middle of a block,
then an explicit inner block can be used,
as in the idiom do return end,
because now return is the last statement in its (inner) block.
@@ -1643,70 +1773,73 @@
The for statement has two forms:
-one numeric and one generic.
+one numerical and one generic.
+
+
The numerical for loop
+
-The numeric for loop repeats a block of code while a
-control variable runs through an arithmetic progression.
+The numerical for loop repeats a block of code while a
+control variable goes through an arithmetic progression.
It has the following syntax:
stat ::= for Name ‘=’ exp ‘,’ exp [‘,’ exp] do block end
-The block is repeated for name starting at the value of
-the first exp, until it passes the second exp by steps of the
-third exp.
-More precisely, a for statement like
+The given identifier (Name) defines the control variable,
+which is a new variable local to the loop body (block).
-
- for v = e1, e2, e3 do block end
-
-is equivalent to the code:
-
- do
- local var, limit, step = tonumber(e1), tonumber(e2), tonumber(e3)
- if not (var and limit and step) then error() end
- while (step > 0 and var <= limit) or (step <= 0 and var >= limit) do
- local v = var
- block
- var = var + step
- end
- end
-
-Note the following:
+
+The loop starts by evaluating once the three control expressions.
+Their values are called respectively
+the initial value, the limit, and the step.
+If the step is absent, it defaults to 1.
-
-
-All three control expressions are evaluated only once,
-before the loop starts.
-They must all result in numbers.
-
+
+If both the initial value and the step are integers,
+the loop is done with integers;
+note that the limit may not be an integer.
+Otherwise, the three values are converted to
+floats and the loop is done with floats.
+Beware of floating-point accuracy in this case.
-
-var, limit, and step are invisible variables.
-The names shown here are for explanatory purposes only.
-
-
-If the third expression (the step) is absent,
-then a step of 1 is used.
-
+
+After that initialization,
+the loop body is repeated with the value of the control variable
+going through an arithmetic progression,
+starting at the initial value,
+with a common difference given by the step.
+A negative step makes a decreasing sequence;
+a step equal to zero raises an error.
+The loop continues while the value is less than
+or equal to the limit
+(greater than or equal to for a negative step).
+If the initial value is already greater than the limit
+(or less than, if the step is negative),
+the body is not executed.
-
-You can use break to exit a for loop.
-
-
-The loop variable v is local to the loop;
-you cannot use its value after the for ends or is broken.
-If you need this value,
-assign it to another variable before breaking or exiting the loop.
-
+
+For integer loops,
+the control variable never wraps around;
+instead, the loop ends in case of an overflow.
-
+
+
+You should not change the value of the control variable
+during the loop.
+If you need its value after the loop,
+assign it to another variable before exiting the loop.
+
+
+
+
+
+
The generic for loop
The generic for statement works over functions,
@@ -1722,49 +1855,50 @@
- for var_1, ···, var_n in explist do block end
+ for var_1, ···, var_n in explist do body end
-is equivalent to the code:
+works as follows.
-
- do
- local f, s, var = explist
- while true do
- local var_1, ···, var_n = f(s, var)
- if var_1 == nil then break end
- var = var_1
- block
- end
- end
-
-Note the following:
-
+
+The names var_i declare loop variables local to the loop body.
+The first of these variables is the control variable.
-
-explist is evaluated only once.
-Its results are an iterator function,
+
+
+The loop starts by evaluating explist
+to produce four values:
+an iterator function,
a state,
-and an initial value for the first iterator variable.
-
+an initial value for the control variable,
+and a closing value.
-
-f, s, and var are invisible variables.
-The names are here for explanatory purposes only.
-
-
-You can use break to exit a for loop.
-
+
+Then, at each iteration,
+Lua calls the iterator function with two arguments:
+the state and the control variable.
+The results from this call are then assigned to the loop variables,
+following the rules of multiple assignments (see §3.3.3).
+If the control variable becomes nil,
+the loop terminates.
+Otherwise, the body is executed and the loop goes
+to the next iteration.
+
+
+
+The closing value behaves like a
+to-be-closed variable (see §3.3.8),
+which can be used to release resources when the loop ends.
+Otherwise, it does not interfere with the loop.
+
+
+
+You should not change the value of the control variable
+during the loop.
+
-
-The loop variables var_i are local to the loop;
-you cannot use their values after the for ends.
-If you need these values,
-then assign them to other variables before breaking or exiting the loop.
-
In this case, all returned values are thrown away.
-Function calls are explained in §3.4.9.
+Function calls are explained in §3.4.10.
@@ -1785,16 +1919,32 @@
Local variables can be declared anywhere inside a block.
-The declaration can include an initial assignment:
+The declaration can include an initialization:
- stat ::= local namelist [‘=’ explist]
+ stat ::= local attnamelist [‘=’ explist]
+ attnamelist ::= Name attrib {‘,’ Name attrib}
If present, an initial assignment has the same semantics
of a multiple assignment (see §3.3.3).
Otherwise, all variables are initialized with nil.
+
+Each variable name may be postfixed by an attribute
+(a name between angle brackets):
+
+
+ attrib ::= [‘<’ Name ‘>’]
+
+There are two possible attributes:
+const, which declares a constant variable,
+that is, a variable that cannot be assigned to
+after its initialization;
+and close, which declares a to-be-closed variable (see §3.3.8).
+A list of variables can contain at most one to-be-closed variable.
+
+
A chunk is also a block (see §3.3.2),
and so local variables can be declared in a chunk outside any explicit block.
@@ -1807,18 +1957,81 @@
+A to-be-closed variable behaves like a constant local variable,
+except that its value is closed whenever the variable
+goes out of scope, including normal block termination,
+exiting its block by break/goto/return,
+or exiting by an error.
+
+
+
+Here, to close a value means
+to call its __close metamethod.
+When calling the metamethod,
+the value itself is passed as the first argument
+and the error object that caused the exit (if any)
+is passed as a second argument;
+if there was no error, the second argument is nil.
+
+
+
+The value assigned to a to-be-closed variable
+must have a __close metamethod
+or be a false value.
+(nil and false are ignored as to-be-closed values.)
+
+
+
+If several to-be-closed variables go out of scope at the same event,
+they are closed in the reverse order that they were declared.
+
+
+
+If there is any error while running a closing method,
+that error is handled like an error in the regular code
+where the variable was defined.
+After an error,
+the other pending closing methods will still be called.
+
+
+
+If a coroutine yields and is never resumed again,
+some variables may never go out of scope,
+and therefore they will never be closed.
+(These variables are the ones created inside the coroutine
+and in scope at the point where the coroutine yielded.)
+Similarly, if a coroutine ends with an error,
+it does not unwind its stack,
+so it does not close any variable.
+In both cases,
+you can either use finalizers
+or call coroutine.close to close the variables.
+However, if the coroutine was created
+through coroutine.wrap,
+then its corresponding function will close the coroutine
+in case of errors.
+
+
+
+
+
-Numbers and literal strings are explained in §3.1;
+Numerals and literal strings are explained in §3.1;
variables are explained in §3.2;
-function definitions are explained in §3.4.10;
-function calls are explained in §3.4.9;
-table constructors are explained in §3.4.8.
+function definitions are explained in §3.4.11;
+function calls are explained in §3.4.10;
+table constructors are explained in §3.4.9.
Vararg expressions,
denoted by three dots ('...'), can only be used when
-directly inside a vararg function;
-they are explained in §3.4.10.
+directly inside a variadic function;
+they are explained in §3.4.11.
Binary operators comprise arithmetic operators (see §3.4.1),
-relational operators (see §3.4.3), logical operators (see §3.4.4),
-and the concatenation operator (see §3.4.5).
+bitwise operators (see §3.4.2),
+relational operators (see §3.4.4), logical operators (see §3.4.5),
+and the concatenation operator (see §3.4.6).
Unary operators comprise the unary minus (see §3.4.1),
-the unary not (see §3.4.4),
-and the unary length operator (see §3.4.6).
+the unary bitwise NOT (see §3.4.2),
+the unary logical not (see §3.4.5),
+and the unary length operator (see §3.4.7).
+
+
+
+
+
+Lua supports the following arithmetic operators:
+
+
+
+: addition
+
-: subtraction
+
*: multiplication
+
/: float division
+
//: floor division
+
%: modulo
+
^: exponentiation
+
-: unary minus
+
-Both function calls and vararg expressions can result in multiple values.
-If a function call is used as a statement (see §3.3.6),
-then its return list is adjusted to zero elements,
-thus discarding all returned values.
-If an expression is used as the last (or the only) element
-of a list of expressions,
-then no adjustment is made
-(unless the expression is enclosed in parentheses).
-In all other contexts,
-Lua adjusts the result list to one element,
-discarding all values except the first one.
+With the exception of exponentiation and float division,
+the arithmetic operators work as follows:
+If both operands are integers,
+the operation is performed over integers and the result is an integer.
+Otherwise, if both operands are numbers,
+then they are converted to floats,
+the operation is performed following the machine's rules
+for floating-point arithmetic
+(usually the IEEE 754 standard),
+and the result is a float.
+(The string library coerces strings to numbers in
+arithmetic operations; see §3.4.3 for details.)
-Here are some examples:
+Exponentiation and float division (/)
+always convert their operands to floats
+and the result is always a float.
+Exponentiation uses the ISO C function pow,
+so that it works for non-integer exponents too.
-
- f() -- adjusted to 0 results
- g(f(), x) -- f() is adjusted to 1 result
- g(x, f()) -- g gets x plus all results from f()
- a,b,c = f(), x -- f() is adjusted to 1 result (c gets nil)
- a,b = ... -- a gets the first vararg parameter, b gets
- -- the second (both a and b can get nil if there
- -- is no corresponding vararg parameter)
-
- a,b,c = x, f() -- f() is adjusted to 2 results
- a,b,c = f() -- f() is adjusted to 3 results
- return f() -- returns all results from f()
- return ... -- returns all received vararg parameters
- return x,y,f() -- returns x, y, and all results from f()
- {f()} -- creates a list with all results from f()
- {...} -- creates a list with all vararg parameters
- {f(), nil} -- f() is adjusted to 1 result
-
-Any expression enclosed in parentheses always results in only one value.
-Thus,
-(f(x,y,z)) is always a single value,
-even if f returns several values.
-(The value of (f(x,y,z)) is the first value returned by f
-or nil if f does not return any values.)
+Floor division (//) is a division
+that rounds the quotient towards minus infinity,
+resulting in the floor of the division of its operands.
+
+Modulo is defined as the remainder of a division
+that rounds the quotient towards minus infinity (floor division).
-
-Lua supports the usual arithmetic operators:
-the binary + (addition),
-- (subtraction), * (multiplication),
-/ (division), % (modulo), and ^ (exponentiation);
-and unary - (mathematical negation).
-If the operands are numbers, or strings that can be converted to
-numbers (see §3.4.2),
-then all operations have the usual meaning.
-Exponentiation works for any exponent.
-For instance, x^(-0.5) computes the inverse of the square root of x.
-Modulo is defined as
-
- a % b == a - math.floor(a/b)*b
-
-That is, it is the remainder of a division that rounds
-the quotient towards minus infinity.
+
+In case of overflows in integer arithmetic,
+all operations wrap around.
+
-Lua provides automatic conversion between
-string and number values at run time.
-Any arithmetic operation applied to a string tries to convert
-this string to a number, following the rules of the Lua lexer.
-(The string may have leading and trailing spaces and a sign.)
-Conversely, whenever a number is used where a string is expected,
-the number is converted to a string, in a reasonable format.
-For complete control over how numbers are converted to strings,
-use the format function from the string library
-(see string.format).
+Both right and left shifts fill the vacant bits with zeros.
+Negative displacements shift to the other direction;
+displacements with absolute values equal to or higher than
+the number of bits in an integer
+result in zero (as all bits are shifted out).
-
+Lua provides some automatic conversions between some
+types and representations at run time.
+Bitwise operators always convert float operands to integers.
+Exponentiation and float division
+always convert integer operands to floats.
+All other arithmetic operations applied to mixed numbers
+(integers and floats) convert the integer operand to a float.
+The C API also converts both integers to floats and
+floats to integers, as needed.
+Moreover, string concatenation accepts numbers as arguments,
+besides strings.
-
- == ~= < > <= >=
-
+
+
+In a conversion from integer to float,
+if the integer value has an exact representation as a float,
+that is the result.
+Otherwise,
+the conversion gets the nearest higher or
+the nearest lower representable value.
+This kind of conversion never fails.
+
+
+
+The conversion from float to integer
+checks whether the float has an exact representation as an integer
+(that is, the float has an integral value and
+it is in the range of integer representation).
+If it does, that representation is the result.
+Otherwise, the conversion fails.
+
+
+
+Several places in Lua coerce strings to numbers when necessary.
+In particular,
+the string library sets metamethods that try to coerce
+strings to numbers in all arithmetic operations.
+If the conversion fails,
+the library calls the metamethod of the other operand
+(if present) or it raises an error.
+Note that bitwise operators do not do this coercion.
+
+
+
+It is always a good practice not to rely on the
+implicit coercions from strings to numbers,
+as they are not always applied;
+in particular, "1"==1 is false and "1"<1 raises an error
+(see §3.4.4).
+These coercions exist mainly for compatibility and may be removed
+in future versions of the language.
+
+
+
+A string is converted to an integer or a float
+following its syntax and the rules of the Lua lexer.
+The string may have also leading and trailing whitespaces and a sign.
+All conversions from strings to numbers
+accept both a dot and the current locale mark
+as the radix character.
+(The Lua lexer, however, accepts only a dot.)
+If the string is not a valid numeral,
+the conversion fails.
+If necessary, the result of this first step is then converted
+to a specific number subtype following the previous rules
+for conversions between floats and integers.
+
+
+
+The conversion from numbers to strings uses a
+non-specified human-readable format.
+To convert numbers to strings in any specific way,
+use the function string.format.
+
+
+
+
+
+
Equality (==) first compares the type of its operands.
If the types are different, then the result is false.
Otherwise, the values of the operands are compared.
-Numbers and strings are compared in the usual way.
+Strings are equal if they have the same byte content.
+Numbers are equal if they denote the same mathematical value.
+
+
+
Tables, userdata, and threads
are compared by reference:
two objects are considered equal only if they are the same object.
Every time you create a new object
-(a table, userdata, or thread),
+(a table, a userdata, or a thread),
this new object is different from any previously existing object.
-Closures with the same reference are always equal.
-Closures with any detectable difference
+A function is always equal to itself.
+Functions with any detectable difference
(different behavior, different definition) are always different.
+Functions created at different times but with no detectable differences
+may be classified as equal or not
+(depending on internal caching details).
You can change the way that Lua compares tables and userdata
-by using the "eq" metamethod (see §2.4).
+by using the __eq metamethod (see §2.4).
-The conversion rules of §3.4.2
-do not apply to equality comparisons.
+Equality comparisons do not convert strings to numbers
+or vice versa.
Thus, "0"==0 evaluates to false,
and t[0] and t["0"] denote different
entries in a table.
@@ -1979,19 +2285,27 @@
The order operators work as follows.
-If both arguments are numbers, then they are compared as such.
+If both arguments are numbers,
+then they are compared according to their mathematical values,
+regardless of their subtypes.
Otherwise, if both arguments are strings,
then their values are compared according to the current locale.
-Otherwise, Lua tries to call the "lt" or the "le"
+Otherwise, Lua tries to call the __lt or the __le
metamethod (see §2.4).
A comparison a > b is translated to b < a
and a >= b is translated to b <= a.
+
+Following the IEEE 754 standard,
+the special value NaN is considered neither less than,
+nor equal to, nor greater than any value, including itself.
+
-
The disjunction operator or returns its first argument
if this value is different from nil and false;
otherwise, or returns its second argument.
-Both and and or use short-cut evaluation;
+Both and and or use short-circuit evaluation;
that is,
the second operand is evaluated only if necessary.
Here are some examples:
@@ -2021,64 +2335,95 @@
The string concatenation operator in Lua is
denoted by two dots ('..').
-If both operands are strings or numbers, then they are converted to
-strings according to the rules mentioned in §3.4.2.
+If both operands are strings or numbers,
+then the numbers are converted to strings
+in a non-specified format (see §3.4.3).
Otherwise, the __concat metamethod is called (see §2.4).
-
The length operator is denoted by the unary prefix operator #.
-The length of a string is its number of bytes
-(that is, the usual meaning of string length when each
-character is one byte).
-A program can modify the behavior of the length operator for
-any value but strings through the __len metamethod (see §2.4).
+The length of a string is its number of bytes.
+(That is the usual meaning of string length when each
+character is one byte.)
-Unless a __len metamethod is given,
-the length of a table t is only defined if the
-table is a sequence,
-that is,
-the set of its positive numeric keys is equal to {1..n}
-for some integer n.
-In that case, n is its length.
-Note that a table like
+The length operator applied on a table
+returns a border in that table.
+A border in a table t is any non-negative integer
+that satisfies the following condition:
- {10, 20, nil, 40}
+ (border == 0 or t[border] ~= nil) and
+ (t[border + 1] == nil or border == math.maxinteger)
-is not a sequence, because it has the key 4
-but does not have the key 3.
-(So, there is no n such that the set {1..n} is equal
-to the set of positive numeric keys of that table.)
-Note, however, that non-numeric keys do not interfere
-with whether a table is a sequence.
+In words,
+a border is any positive integer index present in the table
+that is followed by an absent index,
+plus two limit cases:
+zero, when index 1 is absent;
+and the maximum value for an integer, when that index is present.
+Note that keys that are not positive integers
+do not interfere with borders.
+
+A table with exactly one border is called a sequence.
+For instance, the table {10, 20, 30, 40, 50} is a sequence,
+as it has only one border (5).
+The table {10, 20, 30, nil, 50} has two borders (3 and 5),
+and therefore it is not a sequence.
+(The nil at index 4 is called a hole.)
+The table {nil, 20, 30, nil, nil, 60, nil}
+has three borders (0, 3, and 6),
+so it is not a sequence, too.
+The table {} is a sequence with border 0.
+
+
+
+When t is a sequence,
+#t returns its only border,
+which corresponds to the intuitive notion of the length of the sequence.
+When t is not a sequence,
+#t can return any of its borders.
+(The exact one depends on details of
+the internal representation of the table,
+which in turn can depend on how the table was populated and
+the memory addresses of its non-numeric keys.)
+
+The computation of the length of a table
+has a guaranteed worst time of O(log n),
+where n is the largest integer key in the table.
+
-
Table constructors are expressions that create tables.
Every time a constructor is evaluated, a new table is created.
A constructor can be used to create an empty table
@@ -2121,10 +2470,10 @@
with key exp1 and value exp2.
A field of the form name = exp is equivalent to
["name"] = exp.
-Finally, fields of the form exp are equivalent to
-[i] = exp, where i are consecutive numerical integers,
-starting with 1.
-Fields in the other formats do not affect this counting.
+Fields of the form exp are equivalent to
+[i] = exp, where i are consecutive integers
+starting with 1;
+fields in the other formats do not affect this counting.
For example,
+The order of the assignments in a constructor is undefined.
+(This order would be relevant only when there are repeated keys.)
+
+
If the last field in the list has the form exp
-and the expression is a function call or a vararg expression,
+and the expression is a multires expression,
then all values returned by this expression enter the list consecutively
-(see §3.4.9).
+(see §3.4.12).
If the value of prefixexp has type function,
then this function is called
with the given arguments.
-Otherwise, the prefixexp "call" metamethod is called,
-having as first parameter the value of prefixexp,
+Otherwise, if present,
+the prefixexp __call metamethod is called:
+its first argument is the value of prefixexp,
followed by the original call arguments
(see §2.4).
@@ -2184,7 +2539,7 @@
-can be used to call "methods".
+can be used to emulate methods.
A call v:name(args)
is syntactic sugar for v.name(v,args),
except that v is evaluated only once.
@@ -2196,7 +2551,7 @@
-A call of the form return functioncall is called
-a tail call.
+A call of the form return functioncall not in the
+scope of a to-be-closed variable is called a tail call.
Lua implements proper tail calls
(or proper tail recursion):
-in a tail call,
+In a tail call,
the called function reuses the stack entry of the calling function.
Therefore, there is no limit on the number of nested tail calls that
a program can execute.
However, a tail call erases any debug information about the
calling function.
Note that a tail call only happens with a particular syntax,
-where the return has one single function call as argument;
-this syntax makes the calling function return exactly
-the returns of the called function.
+where the return has one single function call as argument,
+and it is outside the scope of any to-be-closed variable.
+This syntax makes the calling function return exactly
+the returns of the called function,
+without any intervening action.
So, none of the following examples are tail calls:
return (f(x)) -- results adjusted to 1
- return 2 * f(x)
+ return 2 * f(x) -- result multiplied by 2
return x, f(x) -- additional results
f(x); return -- results discarded
return x or f(x) -- results adjusted to 1
@@ -2236,7 +2593,7 @@
A function definition is an executable expression,
whose value has type function.
When Lua precompiles a chunk,
-all its function bodies are precompiled too.
+all its function bodies are precompiled too,
+but they are not created yet.
Then, whenever Lua executes the function definition,
the function is instantiated (or closed).
-This function instance (or closure)
+This function instance, or closure,
is the final value of the expression.
@@ -2311,24 +2669,18 @@
-When a function is called,
-the list of arguments is adjusted to
-the length of the list of parameters,
-unless the function is a vararg function,
+When a Lua function is called,
+it adjusts its list of arguments to
+the length of its list of parameters (see §3.4.12),
+unless the function is a variadic function,
which is indicated by three dots ('...')
at the end of its parameter list.
-A vararg function does not adjust its argument list;
+A variadic function does not adjust its argument list;
instead, it collects all extra arguments and supplies them
to the function through a vararg expression,
which is also written as three dots.
The value of this expression is a list of all actual extra arguments,
-similar to a function with multiple results.
-If a vararg expression is used inside another expression
-or in the middle of a list of expressions,
-then its return list is adjusted to one element.
-If the expression is used as the last element of a list of expressions,
-then no adjustment is made
-(unless that last expression is enclosed in parentheses).
+similar to a function with multiple results (see §3.4.12).
There is a system-dependent limit on the number of values
that a function may return.
-This limit is guaranteed to be larger than 1000.
+This limit is guaranteed to be greater than 1000.
The colon syntax
-is used for defining methods,
-that is, functions that have an implicit extra parameter self.
+is used to emulate methods,
+adding an implicit extra parameter self to the function.
Thus, the statement
-
+Both function calls and vararg expressions can result in multiple values.
+These expressions are called multires expressions.
+
+
+
+When a multires expression is used as the last element
+of a list of expressions,
+all results from the expression are added to the
+list of values produced by the list of expressions.
+Note that a single expression
+in a place that expects a list of expressions
+is the last expression in that (singleton) list.
+
+
+
+These are the places where Lua expects a list of expressions:
+
+
+
+
A return statement,
+for instance return e1, e2, e3 (see §3.3.4).
+
+
A table constructor,
+for instance {e1, e2, e3} (see §3.4.9).
+
+
The arguments of a function call,
+for instance foo(e1, e2, e3) (see §3.4.10).
+
+
A multiple assignment,
+for instance a , b, c = e1, e2, e3 (see §3.3.3).
+
+
A local declaration,
+for instance local a , b, c = e1, e2, e3 (see §3.3.7).
+
+
The initial values in a generic for loop,
+for instance for k in e1, e2, e3 do ... end (see §3.3.5).
+
+
+In the last four cases,
+the list of values from the list of expressions
+must be adjusted to a specific length:
+the number of parameters in a call to a non-variadic function
+(see §3.4.11),
+the number of variables in a multiple assignment or
+a local declaration,
+and exactly four values for a generic for loop.
+The adjustment follows these rules:
+If there are more values than needed,
+the extra values are thrown away;
+if there are fewer values than needed,
+the list is extended with nil's.
+When the list of expressions ends with a multires expression,
+all results from that expression enter the list of values
+before the adjustment.
+
+
+
+When a multires expression is used
+in a list of expressions without being the last element,
+or in a place where the syntax expects a single expression,
+Lua adjusts the result list of that expression to one element.
+As a particular case,
+the syntax expects a single expression inside a parenthesized expression;
+therefore, adding parentheses around a multires expression
+forces it to produce exactly one result.
+
+
+
+We seldom need to use a vararg expression in a place
+where the syntax expects a single expression.
+(Usually it is simpler to add a regular parameter before
+the variadic part and use that parameter.)
+When there is such a need,
+we recommend assigning the vararg expression
+to a single variable and using that variable
+in its place.
+
+
+
+Here are some examples of uses of mutlres expressions.
+In all cases, when the construction needs
+"the n-th result" and there is no such result,
+it uses a nil.
- t.a.b.c.f = function (self, params) body end
+ print(x, f()) -- prints x and all results from f().
+ print(x, (f())) -- prints x and the first result from f().
+ print(f(), x) -- prints the first result from f() and x.
+ print(1 + f()) -- prints 1 added to the first result from f().
+ local x = ... -- x gets the first vararg argument.
+ x,y = ... -- x gets the first vararg argument,
+ -- y gets the second vararg argument.
+ x,y,z = w, f() -- x gets w, y gets the first result from f(),
+ -- z gets the second result from f().
+ x,y,z = f() -- x gets the first result from f(),
+ -- y gets the second result from f(),
+ -- z gets the third result from f().
+ x,y,z = f(), g() -- x gets the first result from f(),
+ -- y gets the first result from g(),
+ -- z gets the second result from g().
+ x,y,z = (f()) -- x gets the first result from f(), y and z get nil.
+ return f() -- returns all results from f().
+ return x, ... -- returns x and all received vararg arguments.
+ return x,y,f() -- returns x, y, and all results from f().
+ {f()} -- creates a list with all results from f().
+ {...} -- creates a list with all vararg arguments.
+ {f(), 5} -- creates a list with the first result from f() and 5.
The scope of a local variable begins at the first statement after
its declaration and lasts until the last non-void statement
of the innermost block that includes the declaration.
+(Void statements are labels and empty statements.)
Consider the following example:
Because of the lexical scoping rules,
local variables can be freely accessed by functions
defined inside their scope.
-A local variable used by an inner function is called
-an upvalue, or external local variable,
+A local variable used by an inner function is called an upvalue
+(or external local variable, or simply external variable)
inside the inner function.
@@ -2439,9 +2908,9 @@
a = {}
local x = 20
- for i=1,10 do
+ for i = 1, 10 do
local y = 0
- a[i] = function () y=y+1; return x+y end
+ a[i] = function () y = y + 1; return x + y end
end
The loop creates ten closures
@@ -2455,6 +2924,8 @@
As in most C libraries,
-the Lua API functions do not check their arguments for validity or consistency.
+the Lua API functions do not check their arguments
+for validity or consistency.
However, you can change this behavior by compiling Lua
with the macro LUA_USE_APICHECK defined.
+
+The Lua library is fully reentrant:
+it has no global variables.
+It keeps all information it needs in a dynamic structure,
+called the Lua state.
+
+
+
+Each Lua state has one or more threads,
+which correspond to independent, cooperative lines of execution.
+The type lua_State (despite its name) refers to a thread.
+(Indirectly, through the thread, it also refers to the
+Lua state associated to the thread.)
+
+
+
+A pointer to a thread must be passed as the first argument to
+every function in the library, except to lua_newstate,
+which creates a Lua state from scratch and returns a pointer
+to the main thread in the new state.
+
+
+
+
Lua uses a virtual stack to pass values to and from C.
Each element in this stack represents a Lua value
(nil, number, string, etc.).
+Functions in the API can access this stack through the
+Lua state parameter that they receive.
which is independent of previous stacks and of stacks of
C functions that are still active.
This stack initially contains any arguments to the C function
-and it is where the C function pushes its results
+and it is where the C function can store temporary
+Lua values and must push its results
to be returned to the caller (see lua_CFunction).
@@ -2503,8 +3004,8 @@
most query operations in the API do not follow a strict stack discipline.
Instead, they can refer to any element in the stack
by using an index:
-A positive index represents an absolute stack position
-(starting at 1);
+A positive index represents an absolute stack position,
+starting at 1 as the bottom of the stack;
a negative index represents an offset relative to the top of the stack.
More specifically, if the stack has n elements,
then index 1 represents the first element
@@ -2519,38 +3020,44 @@
When you interact with the Lua API,
you are responsible for ensuring consistency.
In particular,
you are responsible for controlling stack overflow.
-You can use the function lua_checkstack
-to ensure that the stack has extra slots when pushing new elements.
+When you call any API function,
+you must ensure the stack has enough room to accommodate the results.
+
+
+
+There is one exception to the above rule:
+When you call a Lua function
+without a fixed number of results (see lua_call),
+Lua ensures that the stack has enough space for all results.
+However, it does not ensure any extra space.
+So, before pushing anything on the stack after such a call
+you should use lua_checkstack.
Whenever Lua calls C,
-it ensures that the stack has at least LUA_MINSTACK extra slots.
+it ensures that the stack has space for
+at least LUA_MINSTACK extra elements;
+that is, you can safely push up to LUA_MINSTACK values into it.
LUA_MINSTACK is defined as 20,
so that usually you do not have to worry about stack space
unless your code has loops pushing elements onto the stack.
-
-
-
-When you call a Lua function
-without a fixed number of results (see lua_call),
-Lua ensures that the stack has enough size for all results,
-but it does not ensure any extra space.
-So, before pushing anything in the stack after such a call
-you should use lua_checkstack.
+Whenever necessary,
+you can use the function lua_checkstack
+to ensure that the stack has enough space for pushing new elements.
-
A valid index is an index that refers to a
-valid position within the stack, that is,
-it lies between 1 and the stack top
-(1 ≤ abs(index) ≤ top).
+position that stores a modifiable Lua value.
+It comprises stack indices between 1 and the stack top
+(1 ≤ abs(index) ≤ top)
-Usually, functions that need a specific stack position
-(e.g., lua_remove) require valid indices.
+plus pseudo-indices,
+which represent some positions that are accessible to C code
+but that are not in the stack.
+Pseudo-indices are used to access the registry (see §4.3)
+and the upvalues of a C function (see §4.2).
-Functions that do not need a specific stack position,
-but only a value in the stack (e.g., query functions),
+Functions that do not need a specific mutable position,
+but only a value (e.g., query functions),
can be called with acceptable indices.
-An acceptable index refers to a position within
-the space allocated for the stack,
+An acceptable index can be any valid index,
+but it also can be any positive index after the stack top
+within the space allocated for the stack,
that is, indices up to the stack size.
-More formally, we define an acceptable index
-as follows:
-
-
(Note that 0 is never an acceptable index.)
-When a function is called,
-its stack size is top + LUA_MINSTACK.
-You can change its stack size through function lua_checkstack.
+Indices to upvalues (see §4.2) greater than the real number
+of upvalues in the current C function are also acceptable (but invalid).
+Except when noted otherwise,
+functions in the API work with acceptable indices.
Acceptable indices serve to avoid extra tests
against the stack top when querying the stack.
For instance, a C function can query its third argument
-without the need to first check whether there is a third argument,
+without the need to check whether there is a third argument,
that is, without the need to check whether 3 is a valid index.
For functions that can be called with acceptable indices,
any non-valid index is treated as if it
-contains a value of a virtual type LUA_TNONE.
+contains a value of a virtual type LUA_TNONE,
+which behaves like a nil value.
+
+
+
+
-Unless otherwise noted,
-any function that accepts valid indices also accepts pseudo-indices,
-which represent some Lua values that are accessible to C code
-but which are not in the stack.
-Pseudo-indices are used to access the registry
-and the upvalues of a C function (see §4.4).
+Several functions in the API return pointers (const char*)
+to Lua strings in the stack.
+(See lua_pushfstring, lua_pushlstring,
+lua_pushstring, and lua_tolstring.
+See also luaL_checklstring, luaL_checkstring,
+and luaL_tolstring in the auxiliary library.)
+
+
+
+In general,
+Lua's garbage collection can free or move internal memory
+and then invalidate pointers to internal strings.
+To allow a safe use of these pointers,
+the API guarantees that any pointer to a string in a stack index
+is valid while the string value at that index is not removed from the stack.
+(It can be moved to another index, though.)
+When the index is a pseudo-index (referring to an upvalue),
+the pointer is valid while the corresponding call is active and
+the corresponding upvalue is not modified.
+
+
+
+Some functions in the debug interface
+also return pointers to strings,
+namely lua_getlocal, lua_getupvalue,
+lua_setlocal, and lua_setupvalue.
+For these functions, the pointer is guaranteed to
+be valid while the caller function is active and
+the given closure (if one was given) is in the stack.
+
+
+
+Except for these guarantees,
+the garbage collector is free to invalidate
+any pointer to internal strings.
+
+
-
Whenever a C function is called,
its upvalues are located at specific pseudo-indices.
These pseudo-indices are produced by the macro
-lua_upvalueindex.
-The first value associated with a function is at position
+lua_upvalueindex.
+The first upvalue associated with a function is at index
lua_upvalueindex(1), and so on.
Any access to lua_upvalueindex(n),
where n is greater than the number of upvalues of the
-current function (but not greater than 256),
-produces an acceptable (but invalid) index.
+current function
+(but not greater than 256,
+which is one plus the maximum number of upvalues in a closure),
+produces an acceptable but invalid index.
+
+A C closure can also change the values
+of its corresponding upvalues.
+
-
Lua provides a registry,
a predefined table that can be used by any C code to
store whatever Lua values it needs to store.
-The registry table is always located at pseudo-index
+The registry table is always accessible at pseudo-index
LUA_REGISTRYINDEX.
Any C library can store data into this table,
-but it should take care to choose keys
+but it must take care to choose keys
that are different from those used
by other libraries, to avoid collisions.
Typically, you should use as key a string containing your library name,
or a light userdata with the address of a C object in your code,
or any Lua object created by your code.
-As with global names,
+As with variable names,
string keys starting with an underscore followed by
uppercase letters are reserved for Lua.
-The integer keys in the registry are used by the reference mechanism,
-implemented by the auxiliary library,
+The integer keys in the registry are used
+by the reference mechanism (see luaL_ref)
and by some predefined values.
-Therefore, integer keys should not be used for other purposes.
+Therefore, integer keys in the registry
+must not be used for other purposes.
Internally, Lua uses the C longjmp facility to handle errors.
-(You can also choose to use exceptions if you use C++;
-see file luaconf.h.)
-When Lua faces any error
-(such as a memory allocation error, type errors, syntax errors,
-and runtime errors)
+(Lua will use exceptions if you compile it as C++;
+search for LUAI_THROW in the source code for details.)
+When Lua faces any error,
+such as a memory allocation error or a type error,
it raises an error;
that is, it does a long jump.
A protected environment uses setjmp
@@ -2704,6 +3255,18 @@
any error jumps to the most recent active recovery point.
+
+Inside a C function you can raise an error explicitly
+by calling lua_error.
+
+
+
+Most functions in the API can raise an error,
+for instance due to a memory allocation error.
+The documentation for each function indicates whether
+it can raise errors.
+
+
If an error happens outside any protected environment,
Lua calls a panic function (see lua_atpanic)
@@ -2714,37 +3277,78 @@
(e.g., doing a long jump to your own recovery point outside Lua).
+
+The panic function,
+as its name implies,
+is a mechanism of last resort.
+Programs should avoid it.
+As a general rule,
+when a C function is called by Lua with a Lua state,
+it can do whatever it wants on that Lua state,
+as it should be already protected.
+However,
+when C code operates on other Lua states
+(e.g., a Lua-state argument to the function,
+a Lua state stored in the registry, or
+the result of lua_newthread),
+it should use them only in API calls that cannot raise errors.
+
+
The panic function runs as if it were a message handler (see §2.3);
-in particular, the error message is at the top of the stack.
-However, there is no guarantees about stack space.
+in particular, the error object is on the top of the stack.
+However, there is no guarantee about stack space.
To push anything on the stack,
-the panic function should first check the available space (see §4.2).
+the panic function must first check the available space (see §4.1.1).
-
-Most functions in the API can throw an error,
-for instance due to a memory allocation error.
-The documentation for each function indicates whether
-it can throw errors.
+
+
-Inside a C function you can throw an error by calling lua_error.
+Several functions that report errors in the API use the following
+status codes to indicate different kinds of errors or other conditions:
+
+
Internally, Lua uses the C longjmp facility to yield a coroutine.
-Therefore, if a function foo calls an API function
+Therefore, if a C function foo calls an API function
and this API function yields
(directly or indirectly by calling another function that yields),
Lua cannot return to foo any more,
-because the longjmp removes its frame from the C stack.
+because the longjmp removes its frame from the C stack.
except for three functions:
lua_yieldk, lua_callk, and lua_pcallk.
All those functions receive a continuation function
-(as a parameter called k) to continue execution after a yield.
+(as a parameter named k) to continue execution after a yield.
We need to set some terminology to explain continuations.
-We have a C function called from Lua which we will call
+We have a C function called from Lua which we will call
the original function.
This original function then calls one of those three functions in the C API,
which we will call the callee function,
that then yields the current thread.
-(This can happen when the callee function is lua_yieldk,
+This can happen when the callee function is lua_yieldk,
or when the callee function is either lua_callk or lua_pcallk
-and the function called by them yields.)
+and the function called by them yields.
it eventually will finish running the callee function.
However,
the callee function cannot return to the original function,
-because its frame in the C stack was destroyed by the yield.
+because its frame in the C stack was destroyed by the yield.
Instead, Lua calls a continuation function,
which was given as an argument to the callee function.
As the name implies,
@@ -2782,6 +3386,81 @@
+As an illustration, consider the following function:
+
+
+ int original_function (lua_State *L) {
+ ... /* code 1 */
+ status = lua_pcall(L, n, m, h); /* calls Lua */
+ ... /* code 2 */
+ }
+
+Now we want to allow
+the Lua code being run by lua_pcall to yield.
+First, we can rewrite our function like here:
+
+
+ int k (lua_State *L, int status, lua_KContext ctx) {
+ ... /* code 2 */
+ }
+
+ int original_function (lua_State *L) {
+ ... /* code 1 */
+ return k(L, lua_pcall(L, n, m, h), ctx);
+ }
+
+In the above code,
+the new function k is a
+continuation function (with type lua_KFunction),
+which should do all the work that the original function
+was doing after calling lua_pcall.
+Now, we must inform Lua that it must call k if the Lua code
+being executed by lua_pcall gets interrupted in some way
+(errors or yielding),
+so we rewrite the code as here,
+replacing lua_pcall by lua_pcallk:
+
+
+ int original_function (lua_State *L) {
+ ... /* code 1 */
+ return k(L, lua_pcallk(L, n, m, h, ctx2, k), ctx1);
+ }
+
+Note the external, explicit call to the continuation:
+Lua will call the continuation only if needed, that is,
+in case of errors or resuming after a yield.
+If the called function returns normally without ever yielding,
+lua_pcallk (and lua_callk) will also return normally.
+(Of course, instead of calling the continuation in that case,
+you can do the equivalent work directly inside the original function.)
+
+
+
+Besides the Lua state,
+the continuation function has two other parameters:
+the final status of the call and the context value (ctx) that
+was passed originally to lua_pcallk.
+Lua does not use this context value;
+it only passes this value from the original function to the
+continuation function.
+For lua_pcallk,
+the status is the same value that would be returned by lua_pcallk,
+except that it is LUA_YIELD when being executed after a yield
+(instead of LUA_OK).
+For lua_yieldk and lua_callk,
+the status is always LUA_YIELD when Lua calls the continuation.
+(For these two functions,
+Lua will not call the continuation in case of errors,
+because they do not handle errors.)
+Similarly, when using lua_callk,
+you should call the continuation function
+with LUA_OK as the status.
+(For lua_yieldk, there is not much point in calling
+directly the continuation function,
+because lua_yieldk usually does not return.)
+
+
Lua treats the continuation function as if it were the original function.
The continuation function receives the same Lua stack
@@ -2795,15 +3474,10 @@
depending on the situation;
an interrogation mark '?' means that
we cannot know how many elements the function pops/pushes
-by looking only at its arguments
-(e.g., they may depend on what is on the stack).
+by looking only at its arguments.
+(For instance, they may depend on what is in the stack.)
The third field, x,
-tells whether the function may throw errors:
-'-' means the function never throws any error;
-'e' means the function may throw errors;
-'v' means the function may throw an error on purpose.
+tells whether the function may raise errors:
+'-' means the function never raises any error;
+'m' means the function may raise only out-of-memory errors;
+'v' means the function may raise the errors explained in the text;
+'e' means the function can run arbitrary Lua code,
+either directly or through metamethods,
+and therefore may raise any errors.
@@ -2838,8 +3515,9 @@
-Converts the acceptable index idx into an absolute index
-(that is, one that does not depend on the stack top).
+Converts the acceptable index idx
+into an equivalent absolute index
+(that is, one that does not depend on the stack size).
@@ -2861,7 +3539,7 @@
ptr, a pointer to the block being allocated/reallocated/freed;
osize, the original size of the block or some code about what
is being allocated;
-nsize, the new size of the block.
+and nsize, the new size of the block.
When nsize is zero,
-the allocator should behave like free
-and return NULL.
+the allocator must behave like free
+and then return NULL.
When nsize is not zero,
-the allocator should behave like realloc.
-The allocator returns NULL
+the allocator must behave like realloc.
+In particular, the allocator returns NULL
if and only if it cannot fulfill the request.
-Lua assumes that the allocator never fails when
-osize >= nsize.
-Note that Standard C ensures
+Note that ISO C ensures
that free(NULL) has no effect and that
-realloc(NULL, size) is equivalent to malloc(size).
-This code assumes that realloc does not fail when shrinking a block.
-(Although Standard C does not ensure this behavior,
-it seems to be a safe assumption.)
+realloc(NULL,size) is equivalent to malloc(size).
@@ -2932,10 +3605,10 @@
-Performs an arithmetic operation over the two values
-(or one, in the case of negation)
+Performs an arithmetic or bitwise operation over the two values
+(or one, in the case of negations)
at the top of the stack,
-with the value at the top being the second operand,
+with the value on the top being the second operand,
pops these values, and pushes the result of the operation.
The function follows the semantics of the corresponding Lua operator
(that is, it may call metamethods).
@@ -2949,10 +3622,17 @@
Calls a function.
+Like regular Lua calls,
+lua_call respects the __call metamethod.
+So, here the word "function"
+means any callable value.
-To call a function you must use the following protocol:
+To do a call you must use the following protocol:
first, the function to be called is pushed onto the stack;
-then, the arguments to the function are pushed
+then, the arguments to the call are pushed
in direct order;
that is, the first argument is pushed first.
Finally you call lua_call;
nargs is the number of arguments that you pushed onto the stack.
-All arguments and the function value are popped from the stack
-when the function is called.
-The function results are pushed onto the stack when the function returns.
+When the function returns,
+all arguments and the function value are popped
+and the call results are pushed onto the stack.
The number of results is adjusted to nresults,
unless nresults is LUA_MULTRET.
-In this case, all results from the function are pushed.
-Lua takes care that the returned values fit into the stack space.
+In this case, all results from the function are pushed;
+Lua takes care that the returned values fit into the stack space,
+but it does not ensure any extra space in the stack.
The function results are pushed onto the stack in direct order
(the first result is pushed first),
so that after the call the last result is on the top of the stack.
-Any error inside the called function is propagated upwards
+Any error while calling and running the function is propagated upwards
(with a longjmp).
@@ -3014,7 +3699,7 @@
lua_call(L, 3, 1); /* call 'f' with 3 arguments and 1 result */
lua_setglobal(L, "a"); /* set global 'a' */
-Note that the code above is "balanced":
+Note that the code above is balanced:
at its end, the stack is back to its original configuration.
This is considered good programming practice.
@@ -3032,12 +3717,15 @@
void lua_callk (lua_State *L, int nargs, int nresults, int ctx,
- lua_CFunction k);
+
void lua_callk (lua_State *L,
+ int nargs,
+ int nresults,
+ lua_KContext ctx,
+ lua_KFunction k);
This function behaves exactly like lua_call,
-but allows the called function to yield (see §4.7).
+but allows the called function to yield (see §4.5).
@@ -3062,7 +3750,7 @@
and its last argument is at index lua_gettop(L).
To return values to Lua, a C function just pushes them onto the stack,
in direct order (the first result is pushed first),
-and returns the number of results.
+and returns in C the number of results.
Any other value in the stack below the results will be properly
discarded by Lua.
Like a Lua function, a C function called by Lua can also return
@@ -3071,16 +3759,16 @@
As an example, the following function receives a variable number
-of numerical arguments and returns their average and sum:
+of numeric arguments and returns their average and their sum:
static int foo (lua_State *L) {
int n = lua_gettop(L); /* number of arguments */
- lua_Number sum = 0;
+ lua_Number sum = 0.0;
int i;
for (i = 1; i <= n; i++) {
if (!lua_isnumber(L, i)) {
- lua_pushstring(L, "incorrect argument");
+ lua_pushliteral(L, "incorrect argument");
lua_error(L);
}
sum += lua_tonumber(L, i);
@@ -3096,16 +3784,18 @@
-Ensures that there are at least extra free stack slots in the stack.
+Ensures that the stack has space for at least n extra elements,
+that is, that you can safely push up to n values into it.
It returns false if it cannot fulfill the request,
-because it would cause the stack to be larger than a fixed maximum size
-(typically at least a few thousand elements) or
-because it cannot allocate memory for the new stack size.
+either because it would cause the stack
+to be greater than a fixed maximum size
+(typically at least several thousand elements) or
+because it cannot allocate memory for the extra space.
This function never shrinks the stack;
-if the stack is already larger than the new size,
+if the stack already has space for the extra elements,
it is left unchanged.
@@ -3117,14 +3807,69 @@
-Destroys all objects in the given Lua state
-(calling the corresponding garbage-collection metamethods, if any)
+Close all active to-be-closed variables in the main thread,
+release all objects in the given Lua state
+(calling the corresponding garbage-collection metamethods, if any),
and frees all dynamic memory used by this state.
+
+
+
On several platforms, you may not need to call this function,
because all resources are naturally released when the host program ends.
On the other hand, long-running programs that create multiple states,
such as daemons or web servers,
-might need to close states as soon as they are not needed.
+will probably need to close states as soon as they are not needed.
+
+
+
+
+
+
+Close the to-be-closed slot at the given index and set its value to nil.
+The index must be the last index previously marked to be closed
+(see lua_toclose) that is still active (that is, not closed yet).
+
+
+
+A __close metamethod cannot yield
+when called through this function.
+
+
+
+(This function was introduced in release 5.4.3.)
+
+
+
+
+
+
int lua_closethread (lua_State *L, lua_State *from);
+
+
+Resets a thread, cleaning its call stack and closing all pending
+to-be-closed variables.
+Returns a status code:
+LUA_OK for no errors in the thread
+(either the original error that stopped the thread or
+errors in closing methods),
+or an error status otherwise.
+In case of error,
+leaves the error object on the top of the stack.
+
+
+
+The parameter from represents the coroutine that is resetting L.
+If there is no such coroutine,
+this parameter can be NULL.
+
+
+
+(This function was introduced in release 5.4.6.)
@@ -3136,12 +3881,12 @@
Compares two Lua values.
-Returns 1 if the value at acceptable index index1 satisfies op
-when compared with the value at acceptable index index2,
+Returns 1 if the value at index index1 satisfies op
+when compared with the value at index index2,
following the semantics of the corresponding Lua operator
(that is, it may call metamethods).
Otherwise returns 0.
-Also returns 0 if any of the indices is non valid.
+Also returns 0 if any of the indices is not valid.
Concatenates the n values at the top of the stack,
-pops them, and leaves the result at the top.
+pops them, and leaves the result on the top.
If n is 1, the result is the single value on the stack
(that is, the function does nothing);
if n is 0, the result is the empty string.
Concatenation is performed following the usual semantics of Lua
-(see §3.4.5).
+(see §3.4.6).
@@ -3180,17 +3925,17 @@
void lua_copy (lua_State *L, int fromidx, int toidx);
-Moves the element at the valid index fromidx
-into the valid index toidx
-without shifting any element
-(therefore replacing the value at that position).
+Copies the element at index fromidx
+into the valid index toidx,
+replacing the value at that position.
+Values at other positions are not affected.
parameter nrec is a hint for how many other elements
the table will have.
Lua may use these hints to preallocate memory for the new table.
-This pre-allocation is useful for performance when you know in advance
+This preallocation may help performance when you know in advance
how many elements the table will have.
Otherwise you can use the function lua_newtable.
@@ -3209,8 +3954,11 @@
-Generates a Lua error.
-The error message (which can actually be a Lua value of any type)
-must be on the stack top.
+Raises a Lua error,
+using the value on the top of the stack as the error object.
This function does a long jump,
and therefore never returns
(see luaL_error).
@@ -3254,8 +4008,8 @@
This function performs several tasks,
-according to the value of the parameter what:
+according to the value of the parameter what.
+For options that need extra arguments,
+they are listed after the option.
-
LUA_GCSTOP:
-stops the garbage collector.
+
LUA_GCCOLLECT:
+Performs a full garbage-collection cycle.
-
LUA_GCRESTART:
-restarts the garbage collector.
+
LUA_GCSTOP:
+Stops the garbage collector.
-
LUA_GCCOLLECT:
-performs a full garbage-collection cycle.
+
LUA_GCRESTART:
+Restarts the garbage collector.
LUA_GCCOUNT:
-returns the current amount of memory (in Kbytes) in use by Lua.
+Returns the current amount of memory (in Kbytes) in use by Lua.
LUA_GCCOUNTB:
-returns the remainder of dividing the current amount of bytes of
+Returns the remainder of dividing the current amount of bytes of
memory in use by Lua by 1024.
-
LUA_GCSTEP:
-performs an incremental step of garbage collection.
-The step "size" is controlled by data
-(larger values mean more steps) in a non-specified way.
-If you want to control the step size
-you must experimentally tune the value of data.
-The function returns 1 if the step finished a
-garbage-collection cycle.
-
-
-
LUA_GCSETPAUSE:
-sets data as the new value
-for the pause of the collector (see §2.5).
-The function returns the previous value of the pause.
-
-
-
LUA_GCSETSTEPMUL:
-sets data as the new value for the step multiplier of
-the collector (see §2.5).
-The function returns the previous value of the step multiplier.
+
LUA_GCSTEP(int stepsize):
+Performs an incremental step of garbage collection,
+corresponding to the allocation of stepsize Kbytes.
LUA_GCISRUNNING:
-returns a boolean that tells whether the collector is running
+Returns a boolean that tells whether the collector is running
(i.e., not stopped).
-
LUA_GCGEN:
-changes the collector to generational mode
-(see §2.5).
+
LUA_GCINC (int pause, int stepmul, stepsize):
+Changes the collector to incremental mode
+with the given parameters (see §2.5.1).
+Returns the previous mode (LUA_GCGEN or LUA_GCINC).
-
LUA_GCINC:
-changes the collector to incremental mode.
-This is the default mode.
+
LUA_GCGEN (int minormul, int majormul):
+Changes the collector to generational mode
+with the given parameters (see §2.5.2).
+Returns the previous mode (LUA_GCGEN or LUA_GCINC).
-
-
-
+
For more details about these options,
see collectgarbage.
+
+This function should not be called by a finalizer.
+
+
@@ -3342,68 +4085,80 @@
Returns the memory-allocation function of a given state.
If ud is not NULL, Lua stores in *ud the
-opaque pointer passed to lua_newstate.
+opaque pointer given when the memory-allocator function was set.
-
int lua_getfield (lua_State *L, int index, const char *k);
+
+
+Pushes onto the stack the value t[k],
+where t is the value at the given index.
+As in Lua, this function may trigger a metamethod
+for the "index" event (see §2.4).
+
+
+
+Returns the type of the pushed value.
+
+
+
+
+
+
-This function is called by a continuation function (see §4.7)
-to retrieve the status of the thread and a context information.
+Returns a pointer to a raw memory area associated with the
+given Lua state.
+The application can use this area for any purpose;
+Lua does not use it for anything.
-When called in the original function,
-lua_getctx always returns LUA_OK
-and does not change the value of its argument ctx.
-When called inside a continuation function,
-lua_getctx returns LUA_YIELD and sets
-the value of ctx to be the context information
-(the value passed as the ctx argument
-to the callee together with the continuation function).
+Each new thread has this area initialized with a copy
+of the area of the main thread.
-When the callee is lua_pcallk,
-Lua may also call its continuation function
-to handle errors during the call.
-That is, upon an error in the function called by lua_pcallk,
-Lua may not return to the original function
-but instead may call the continuation function.
-In that case, a call to lua_getctx will return the error code
-(the value that would be returned by lua_pcallk);
-the value of ctx will be set to the context information,
-as in the case of a yield.
+By default, this area has the size of a pointer to void,
+but you can recompile Lua with a different size for this area.
+(See LUA_EXTRASPACE in luaconf.h.)
-
void lua_getfield (lua_State *L, int index, const char *k);
+
int lua_getglobal (lua_State *L, const char *name);
-Pushes onto the stack the value t[k],
-where t is the value at the given valid index.
-As in Lua, this function may trigger a metamethod
-for the "index" event (see §2.4).
+Pushes onto the stack the value of the global name.
+Returns the type of that value.
-
int lua_geti (lua_State *L, int index, lua_Integer i);
-Pushes onto the stack the value of the global name.
+Pushes onto the stack the value t[i],
+where t is the value at the given index.
+As in Lua, this function may trigger a metamethod
+for the "index" event (see §2.4).
+
+
+
+Returns the type of the pushed value.
@@ -3414,9 +4169,9 @@
-Pushes onto the stack the metatable of the value at the given
-acceptable index.
-If the value does not have a metatable,
+If the value at the given index has a metatable,
+the function pushes that metatable onto the stack and returns 1.
+Otherwise,
the function returns 0 and pushes nothing on the stack.
@@ -3425,21 +4180,25 @@
Pushes onto the stack the value t[k],
-where t is the value at the given valid index
-and k is the value at the top of the stack.
+where t is the value at the given index
+and k is the value on the top of the stack.
-This function pops the key from the stack
-(putting the resulting value in its place).
+This function pops the key from the stack,
+pushing the resulting value in its place.
As in Lua, this function may trigger a metamethod
for the "index" event (see §2.4).
+
+Returns the type of the pushed value.
+
+
@@ -3450,21 +4209,26 @@
Returns the index of the top element in the stack.
Because indices start at 1,
-this result is equal to the number of elements in the stack
-(and so 0 means an empty stack).
+this result is equal to the number of elements in the stack;
+in particular, 0 means an empty stack.
-
int lua_getiuservalue (lua_State *L, int index, int n);
-Pushes onto the stack the Lua value associated with the userdata
-at the given index.
-This Lua value must be a table or nil.
+Pushes onto the stack the n-th user value associated with the
+full userdata at the given index and
+returns the type of the pushed value.
+
+
+
+If the userdata does not have that value,
+pushes nil and returns LUA_TNONE.
@@ -3477,7 +4241,7 @@
Moves the top element into the given valid index,
shifting up the elements above this index to open space.
-Cannot be called with a pseudo-index,
+This function cannot be called with a pseudo-index,
because a pseudo-index is not an actual stack position.
@@ -3485,16 +4249,24 @@
-The type used by the Lua API to represent signed integral values.
+By default this type is long long,
+(usually a 64-bit two-complement integer),
+but that can be changed to long or int
+(usually a 32-bit two-complement integer).
+(See LUA_INT_TYPE in luaconf.h.)
-By default it is a ptrdiff_t,
-which is usually the largest signed integral type the machine handles
-"comfortably".
+Lua also defines the constants
+LUA_MININTEGER and LUA_MAXINTEGER,
+with the minimum and the maximum values that fit in this type.
@@ -3505,7 +4277,7 @@
-Returns 1 if the value at the given acceptable index is a boolean,
+Returns 1 if the value at the given index is a boolean,
and 0 otherwise.
@@ -3517,7 +4289,7 @@
-Returns 1 if the value at the given acceptable index is a C function,
+Returns 1 if the value at the given index is a C function,
and 0 otherwise.
@@ -3529,19 +4301,32 @@
-Returns 1 if the value at the given acceptable index is a function
+Returns 1 if the value at the given index is a function
(either C or Lua), and 0 otherwise.
+
+Returns 1 if the value at the given index is an integer
+(that is, the value is a number and is represented as an integer),
+and 0 otherwise.
+
+
+
+
+
int lua_islightuserdata (lua_State *L, int index);
-Returns 1 if the value at the given acceptable index is a light userdata,
+Returns 1 if the value at the given index is a light userdata,
and 0 otherwise.
@@ -3553,7 +4338,7 @@
-Returns 1 if the value at the given acceptable index is nil,
+Returns 1 if the value at the given index is nil,
and 0 otherwise.
@@ -3565,8 +4350,7 @@
-Returns 1 if the given acceptable index is not valid
-(that is, it refers to an element outside the current stack),
+Returns 1 if the given index is not valid,
and 0 otherwise.
@@ -3578,8 +4362,7 @@
-Returns 1 if the given acceptable index is not valid
-(that is, it refers to an element outside the current stack)
+Returns 1 if the given index is not valid
or if the value at this index is nil,
and 0 otherwise.
@@ -3592,7 +4375,7 @@
-Returns 1 if the value at the given acceptable index is a number
+Returns 1 if the value at the given index is a number
or a string convertible to a number,
and 0 otherwise.
@@ -3605,7 +4388,7 @@
-Returns 1 if the value at the given acceptable index is a string
+Returns 1 if the value at the given index is a string
or a number (which is always convertible to a string),
and 0 otherwise.
@@ -3613,37 +4396,74 @@
-Returns 1 if the value at the given acceptable index is a thread,
-and 0 otherwise.
+The type for continuation-function contexts.
+It must be a numeric type.
+This type is defined as intptr_t
+when intptr_t is available,
+so that it can store pointers too.
+Otherwise, it is defined as ptrdiff_t.
-
typedef int (*lua_KFunction) (lua_State *L, int status, lua_KContext ctx);
-Returns 1 if the value at the given acceptable index is a userdata
-(either full or light), and 0 otherwise.
+Type for continuation functions (see §4.5).
@@ -3654,8 +4474,9 @@
-Returns the "length" of the value at the given acceptable index;
-it is equivalent to the '#' operator in Lua (see §3.4.6).
+Returns the length of the value at the given index.
+It is equivalent to the '#' operator in Lua (see §3.4.7) and
+may trigger a metamethod for the "length" event (see §2.4).
The result is pushed on the stack.
@@ -3667,38 +4488,17 @@
-Loads a Lua chunk (without running it).
+Loads a Lua chunk without running it.
If there are no errors,
lua_load pushes the compiled chunk as a Lua
function on top of the stack.
Otherwise, it pushes an error message.
-
LUA_ERRGCMM:
-error while running a __gc metamethod.
-(This error has no relation with the chunk being loaded.
-It is generated by the garbage collector.)
-
-
-
-
The lua_load function uses a user-supplied reader function
to read the chunk (see lua_Reader).
@@ -3706,8 +4506,8 @@
-The source argument gives a name to the chunk,
-which is used for error messages and in debug information (see §4.9).
+The chunkname argument gives a name to the chunk,
+which is used for error messages and in debug information (see §4.7).
-If the resulting function has one upvalue,
-this upvalue is set to the value of the global environment
-stored at index LUA_RIDX_GLOBALS in the registry (see §4.5).
+lua_load uses the stack internally,
+so the reader function must always leave the stack
+unmodified when returning.
+
+
+
+lua_load can return
+LUA_OK, LUA_ERRSYNTAX, or LUA_ERRMEM.
+The function may also return other values corresponding to
+errors raised by the read function (see §4.4.1).
+
+
+
+If the resulting function has upvalues,
+its first upvalue is set to the value of the global environment
+stored at index LUA_RIDX_GLOBALS in the registry (see §4.3).
When loading main chunks,
this upvalue will be the _ENV variable (see §2.2).
+Other upvalues are initialized with nil.
@@ -3734,11 +4548,12 @@
-Creates a new thread running in a new, independent state.
-Returns NULL if cannot create the thread or the state
+Creates a new independent state and returns its main thread.
+Returns NULL if it cannot create the state
(due to lack of memory).
The argument f is the allocator function;
-Lua does all memory allocation for this state through this function.
+Lua will do all memory allocation for this state
+through this function (see lua_Alloc).
The second argument, ud, is an opaque pointer that Lua
passes to the allocator in every call.
@@ -3747,7 +4562,7 @@
-There is no explicit function to close or to destroy a thread.
Threads are subject to garbage collection,
like any Lua object.
@@ -3779,34 +4593,43 @@
void *lua_newuserdatauv (lua_State *L, size_t size, int nuvalue);
+
+
+This function creates and pushes on the stack a new full userdata,
+with nuvalue associated Lua values, called user values,
+plus an associated block of raw memory with size bytes.
+(The user values can be set and read with the functions
+lua_setiuservalue and lua_getiuservalue.)
+
-This function allocates a new block of memory with the given size,
-pushes onto the stack a new full userdata with the block address,
-and returns this address.
-The host program can freely use this memory.
+The function returns the address of the block of memory.
+Lua ensures that this address is valid as long as
+the corresponding userdata is alive (see §2.5).
+Moreover, if the userdata is marked for finalization (see §2.5.3),
+its address is valid at least until the call to its finalizer.
Pops a key from the stack,
-and pushes a key–value pair from the table at the given index
-(the "next" pair after the given key).
+and pushes a key–value pair from the table at the given index,
+the "next" pair after the given key.
If there are no more elements in the table,
-then lua_next returns 0 (and pushes nothing).
+then lua_next returns 0 and pushes nothing.
-A typical traversal looks like this:
+A typical table traversal looks like this:
/* table is in the stack at index 't' */
@@ -3823,7 +4646,7 @@
While traversing a table,
-do not call lua_tolstring directly on a key,
+avoid calling lua_tolstring directly on a key,
unless you know that the key is actually a string.
Recall that lua_tolstring may change
the value at the given index;
@@ -3831,6 +4654,8 @@
+This function may raise an error if the given key
+is neither nil nor present in the table.
See function next for the caveats of modifying
the table during its traversal.
@@ -3839,13 +4664,37 @@
int lua_numbertointeger (lua_Number n, lua_Integer *p);
-The type of numbers in Lua.
-By default, it is double, but that can be changed in luaconf.h.
-Through this configuration file you can change
-Lua to operate with another type for numbers (e.g., float or long).
+Tries to convert a Lua float to a Lua integer;
+the float n must have an integral value.
+If that value is within the range of Lua integers,
+it is converted to an integer and assigned to *p.
+The macro results in a boolean indicating whether the
+conversion was successful.
+(Note that this range test can be tricky to do
+correctly without this macro, due to rounding.)
+
+
+
+This macro may evaluate its arguments more than once.
@@ -3856,7 +4705,7 @@
lua_pcall behaves exactly like lua_call.
However, if there is any error,
lua_pcall catches it,
-pushes a single value on the stack (the error message),
+pushes a single value on the stack (the error object),
and returns an error code.
Like lua_call,
lua_pcall always removes the function
@@ -3875,53 +4724,28 @@
If msgh is 0,
-then the error message returned on the stack
-is exactly the original error message.
+then the error object returned on the stack
+is exactly the original error object.
Otherwise, msgh is the stack index of a
message handler.
-(In the current implementation, this index cannot be a pseudo-index.)
+(This index cannot be a pseudo-index.)
In case of runtime errors,
-this function will be called with the error message
-and its return value will be the message
+this handler will be called with the error object
+and its return value will be the object
returned on the stack by lua_pcall.
Typically, the message handler is used to add more debug
-information to the error message, such as a stack traceback.
+information to the error object, such as a stack traceback.
Such information cannot be gathered after the return of lua_pcall,
since by then the stack has unwound.
-The lua_pcall function returns one of the following codes
-(defined in lua.h):
-
-
LUA_ERRMEM:
-memory allocation error.
-For such errors, Lua does not call the message handler.
-
-
-
LUA_ERRERR:
-error while running the message handler.
-
-
-
LUA_ERRGCMM:
-error while running a __gc metamethod.
-(This error typically has no relation with the function being called.
-It is generated by the garbage collector.)
-
int lua_pcallk (lua_State *L,
int nargs,
int nresults,
- int errfunc,
- int ctx,
- lua_CFunction k);
+ int msgh,
+ lua_KContext ctx,
+ lua_KFunction k);
This function behaves exactly like lua_pcall,
-but allows the called function to yield (see §4.7).
+except that it allows the called function to yield (see §4.5).
void lua_pushcclosure (lua_State *L, lua_CFunction fn, int n);
Pushes a new C closure onto the stack.
+This function receives a pointer to a C function
+and pushes onto the stack a Lua value of type function that,
+when called, invokes the corresponding C function.
+The parameter n tells how many upvalues this function will have
+(see §4.2).
+
+
+
+Any function to be callable by Lua must
+follow the correct protocol to receive its parameters
+and return its results (see lua_CFunction).
When a C function is created,
it is possible to associate some values with it,
-thus creating a C closure (see §4.4);
-these values are then accessible to the function whenever it is called.
-To associate values with a C function,
-first these values should be pushed onto the stack
-(when there are multiple values, the first value is pushed first).
+the so called upvalues;
+these upvalues are then accessible to the function whenever it is called.
+This association is called a C closure (see §4.2).
+To create a C closure,
+first the initial values for its upvalues must be pushed onto the stack.
+(When there are multiple upvalues, the first value is pushed first.)
Then lua_pushcclosure
is called to create and push the C function onto the stack,
-with the argument n telling how many values should be
+with the argument n telling how many values will be
associated with the function.
lua_pushcclosure also pops these values from the stack.
@@ -3994,9 +4831,9 @@
When n is zero,
-this function creates a light C function,
+this function creates a light C function,
which is just a pointer to the C function.
-In that case, it never throws a memory error.
+In that case, it never raises a memory error.
@@ -4008,60 +4845,54 @@
Pushes a C function onto the stack.
-This function receives a pointer to a C function
-and pushes onto the stack a Lua value of type function that,
-when called, invokes the corresponding C function.
-
-
-
-Any function to be registered in Lua must
-follow the correct protocol to receive its parameters
-and return its results (see lua_CFunction).
-
-
-
Pushes onto the stack a formatted string
-and returns a pointer to this string.
-It is similar to the C function sprintf,
-but has some important differences:
-
-
-
-
-You do not have to allocate space for the result:
+and returns a pointer to this string (see §4.1.3).
+It is similar to the ISO C function sprintf,
+but has two important differences.
+First,
+you do not have to allocate space for the result;
the result is a Lua string and Lua takes care of memory allocation
(and deallocation, through garbage collection).
-
-
-
-The conversion specifiers are quite restricted.
+Second,
+the conversion specifiers are quite restricted.
There are no flags, widths, or precisions.
The conversion specifiers can only be
-'%%' (inserts a '%' in the string),
+'%%' (inserts the character '%'),
'%s' (inserts a zero-terminated string, with no size restrictions),
'%f' (inserts a lua_Number),
-'%p' (inserts a pointer as a hexadecimal numeral),
-'%d' (inserts an int), and
-'%c' (inserts an int as a byte).
-
+'%I' (inserts a lua_Integer),
+'%p' (inserts a pointer),
+'%d' (inserts an int),
+'%c' (inserts an int as a one-byte character), and
+'%U' (inserts a long int as a UTF-8 byte sequence).
+
+
+
+This function may raise errors due to memory overflow
+or an invalid conversion specifier.
+
+
+
+
+
+
-This macro is equivalent to lua_pushlstring,
-but can be used only when s is a literal string.
-It automatically provides the string length.
+This macro is equivalent to lua_pushstring,
+but should be used only when s is a literal string.
+(Lua may optimize this case.)
Pushes the string pointed to by s with size len
onto the stack.
-Lua makes (or reuses) an internal copy of the given string,
+Lua will make or reuse an internal copy of the given string,
so the memory at s can be freed or reused immediately after
the function returns.
The string can contain any binary data,
@@ -4126,7 +4957,7 @@
Pushes the zero-terminated string pointed to by s
onto the stack.
-Lua makes (or reuses) an internal copy of the given string,
+Lua will make or reuse an internal copy of the given string,
so the memory at s can be freed or reused immediately after
the function returns.
-Returns a pointer to the internal copy of the string.
+Returns a pointer to the internal copy of the string (see §4.1.3).
int lua_rawequal (lua_State *L, int index1, int index2);
-Returns 1 if the two values in acceptable indices index1 and
+Returns 1 if the two values in indices index1 and
index2 are primitively equal
-(that is, without calling metamethods).
+(that is, equal without calling the __eq metamethod).
Otherwise returns 0.
-Also returns 0 if any of the indices are non valid.
+Also returns 0 if any of the indices are not valid.
@@ -4232,11 +5063,12 @@
void lua_rawgeti (lua_State *L, int index, int n);
+
int lua_rawgeti (lua_State *L, int index, lua_Integer n);
Pushes onto the stack the value t[n],
-where t is the table at the given valid index.
-The access is raw;
-that is, it does not invoke metamethods.
+where t is the table at the given index.
+The access is raw,
+that is, it does not use the __index metavalue.
+
+
+
+Returns the type of the pushed value.
@@ -4258,14 +5094,18 @@
void lua_rawgetp (lua_State *L, int index, const void *p);
+
int lua_rawgetp (lua_State *L, int index, const void *p);
Pushes onto the stack the value t[k],
-where t is the table at the given valid index and
+where t is the table at the given index and
k is the pointer p represented as a light userdata.
The access is raw;
-that is, it does not invoke metamethods.
+that is, it does not use the __index metavalue.
+
+
+
+Returns the type of the pushed value.
@@ -4273,67 +5113,68 @@
lua_Unsigned lua_rawlen (lua_State *L, int index);
-Returns the raw "length" of the value at the given acceptable index:
+Returns the raw "length" of the value at the given index:
for strings, this is the string length;
for tables, this is the result of the length operator ('#')
with no metamethods;
for userdata, this is the size of the block of memory allocated
-for the userdata;
-for other values, it is 0.
+for the userdata.
+For other values, this call returns 0.
void lua_rawseti (lua_State *L, int index, int n);
+[-1, +0, m]
+
void lua_rawseti (lua_State *L, int index, lua_Integer i);
-Does the equivalent of t[n] = v,
-where t is the table at the given valid index
-and v is the value at the top of the stack.
+Does the equivalent of t[i] = v,
+where t is the table at the given index
+and v is the value on the top of the stack.
This function pops the value from the stack.
-The assignment is raw;
-that is, it does not invoke metamethods.
+The assignment is raw,
+that is, it does not use the __newindex metavalue.
void lua_rawsetp (lua_State *L, int index, const void *p);
-Does the equivalent of t[k] = v,
-where t is the table at the given valid index,
-k is the pointer p represented as a light userdata,
-and v is the value at the top of the stack.
+Does the equivalent of t[p] = v,
+where t is the table at the given index,
+p is encoded as a light userdata,
+and v is the value on the top of the stack.
This function pops the value from the stack.
-The assignment is raw;
-that is, it does not invoke metamethods.
+The assignment is raw,
+that is, it does not use the __newindex metavalue.
@@ -4346,8 +5187,8 @@
The reader function used by lua_load.
-Every time it needs another piece of the chunk,
-lua_load calls the reader,
+Every time lua_load needs another piece of the chunk,
+it calls the reader,
passing along its data parameter.
The reader must return a pointer to a block of memory
with a new piece of the chunk
@@ -4366,7 +5207,7 @@
Removes the element at the given valid index,
shifting down the elements above this index to fill the gap.
-Cannot be called with a pseudo-index,
+This function cannot be called with a pseudo-index,
because a pseudo-index is not an actual stack position.
@@ -4396,48 +5237,62 @@
-Moves the top element into the given position
+Moves the top element into the given valid index
without shifting any element
-(therefore replacing the value at the given position),
+(therefore replacing the value at that given index),
and then pops the top element.
+
int lua_resume (lua_State *L, lua_State *from, int nargs);
+
int lua_resume (lua_State *L, lua_State *from, int nargs,
+ int *nresults);
-Starts and resumes a coroutine in a given thread.
+Starts and resumes a coroutine in the given thread L.
To start a coroutine,
-you push onto the thread stack the main function plus any arguments;
+you push the main function plus any arguments
+onto the empty stack of the thread.
then you call lua_resume,
with nargs being the number of arguments.
This call returns when the coroutine suspends or finishes its execution.
-When it returns, the stack contains all values passed to lua_yield,
-or all values returned by the body function.
+When it returns,
+*nresults is updated and
+the top of the stack contains
+the *nresults values passed to lua_yield
+or returned by the body function.
lua_resume returns
LUA_YIELD if the coroutine yields,
LUA_OK if the coroutine finishes its execution
without errors,
-or an error code in case of errors (see lua_pcall).
-
-
-
+or an error code in case of errors (see §4.4.1).
In case of errors,
-the stack is not unwound,
-so you can use the debug API over it.
-The error message is on the top of the stack.
+the error object is on the top of the stack.
-To resume a coroutine, you put on its stack only the values to
-be passed as results from yield,
+To resume a coroutine,
+you remove the *nresults yielded values from its stack,
+push the values to be passed as results from yield,
and then call lua_resume.
@@ -4450,6 +5305,26 @@
+Rotates the stack elements between the valid index idx
+and the top of the stack.
+The elements are rotated n positions in the direction of the top,
+for a positive n,
+or -n positions in the direction of the bottom,
+for a negative n.
+The absolute value of n must not be greater than the size
+of the slice being rotated.
+This function cannot be called with a pseudo-index,
+because a pseudo-index is not an actual stack position.
+
+
+
+
+
Does the equivalent to t[k] = v,
-where t is the value at the given valid index
-and v is the value at the top of the stack.
+where t is the value at the given index
+and v is the value on the top of the stack.
int lua_setiuservalue (lua_State *L, int index, int n);
+
+
+Pops a value from the stack and sets it as
+the new n-th user value associated to the
+full userdata at the given index.
+Returns 0 if the userdata does not have that value.
+
+
+
+
+
+Pops a table or nil from the stack and
+sets that value as the new metatable for the value at the given index.
+(nil means no metatable.)
+
-Pops a table from the stack and
-sets it as the new metatable for the value at the given
-acceptable index.
+(For historical reasons, this function returns an int,
+which now is always 1.)
@@ -4512,8 +5425,8 @@
Does the equivalent to t[k] = v,
-where t is the value at the given valid index,
-v is the value at the top of the stack,
+where t is the value at the given index,
+v is the value on the top of the stack,
and k is the value just below the top.
@@ -4527,27 +5440,34 @@
-Accepts any acceptable index, or 0,
+Accepts any index, or 0,
and sets the stack top to this index.
-If the new top is larger than the old one,
+If the new top is greater than the old one,
then the new elements are filled with nil.
If index is 0, then all stack elements are removed.
+
+This function can run arbitrary code when removing an index
+marked as to-be-closed from the stack.
+
-
-Pops a table or nil from the stack and sets it as
-the new value associated to the userdata at the given index.
+Sets the warning function to be used by Lua to emit warnings
+(see lua_WarnFunction).
+The ud parameter sets the value ud passed to
+the warning function.
@@ -4582,14 +5502,14 @@
-The status can be 0 (LUA_OK) for a normal thread,
+The status can be LUA_OK for a normal thread,
an error code if the thread finished the execution
of a lua_resume with an error,
-or LUA_YIELD if the thread is suspended.
+or LUA_YIELD if the thread is suspended.
-You can only call functions in threads with status LUA_OK.
+You can call functions only in threads with status LUA_OK.
You can resume threads with status LUA_OK
(to start a new coroutine) or LUA_YIELD
(to resume a coroutine).
@@ -4598,18 +5518,38 @@
+Converts the zero-terminated string s to a number,
+pushes that number into the stack,
+and returns the total size of the string,
+that is, its length plus one.
+The conversion can result in an integer or a float,
+according to the lexical conventions of Lua (see §3.1).
+The string may have leading and trailing whitespaces and a sign.
+If the string is not a valid numeral,
+returns 0 and pushes nothing.
+(Note that the result can be used as a boolean,
+true if the conversion succeeds.)
+
+
+
+
+
-Converts the Lua value at the given acceptable index to a C boolean
+Converts the Lua value at the given index to a C boolean
value (0 or 1).
Like all tests in Lua,
lua_toboolean returns true for any Lua value
different from false and nil;
otherwise it returns false.
-It also returns false when called with a non-valid index.
(If you want to accept only actual boolean values,
use lua_isboolean to test the value's type.)
@@ -4622,7 +5562,7 @@
lua_CFunction lua_tocfunction (lua_State *L, int index);
-Converts a value at the given acceptable index to a C function.
+Converts a value at the given index to a C function.
That value must be a C function;
otherwise, returns NULL.
@@ -4630,6 +5570,48 @@
+Marks the given index in the stack as a
+to-be-closed slot (see §3.3.8).
+Like a to-be-closed variable in Lua,
+the value at that slot in the stack will be closed
+when it goes out of scope.
+Here, in the context of a C function,
+to go out of scope means that the running function returns to Lua,
+or there is an error,
+or the slot is removed from the stack through
+lua_settop or lua_pop,
+or there is a call to lua_closeslot.
+A slot marked as to-be-closed should not be removed from the stack
+by any other function in the API except lua_settop or lua_pop,
+unless previously deactivated by lua_closeslot.
+
+
+
+This function raises an error if the value at the given slot
+neither has a __close metamethod nor is a false value.
+
+
+
+This function should not be called for an index
+that is equal to or below an active to-be-closed slot.
+
+
+
+Note that, both in case of errors and of a regular return,
+by the time the __close metamethod runs,
+the C stack was already unwound,
+so that any automatic C variable declared in the calling function
+(e.g., a buffer) will be out of scope.
+
+
+
+
+
lua_Integer lua_tointegerx (lua_State *L, int index, int *isnum);
-Converts the Lua value at the given acceptable index
+Converts the Lua value at the given index
to the signed integral type lua_Integer.
-The Lua value must be a number or a string convertible to a number
-(see §3.4.2);
+The Lua value must be an integer,
+or a number or string convertible to an integer (see §3.4.3);
otherwise, lua_tointegerx returns 0.
-
-If the number is not an integer,
-it is truncated in some non-specified way.
-
-
If isnum is not NULL,
its referent is assigned a boolean value that
@@ -4668,13 +5645,13 @@
const char *lua_tolstring (lua_State *L, int index, size_t *len);
-Converts the Lua value at the given acceptable index to a C string.
+Converts the Lua value at the given index to a C string.
If len is not NULL,
-it also sets *len with the string length.
+it sets *len with the string length.
The Lua value must be a string or a number;
otherwise, the function returns NULL.
If the value is a number,
@@ -4685,14 +5662,17 @@
-lua_tolstring returns a fully aligned pointer
-to a string inside the Lua state.
+lua_tolstring returns a pointer
+to a string inside the Lua state (see §4.1.3).
This string always has a zero ('\0')
after its last character (as in C),
but can contain other zeros in its body.
-Because Lua has garbage collection,
-there is no guarantee that the pointer returned by lua_tolstring
-will be valid after the corresponding value is removed from the stack.
+
+
+
+This function can raise memory errors only
+when converting a number to a string
+(as then it may create a new string).
@@ -4714,10 +5694,10 @@
lua_Number lua_tonumberx (lua_State *L, int index, int *isnum);
-Converts the Lua value at the given acceptable index
+Converts the Lua value at the given index
to the C type lua_Number (see lua_Number).
The Lua value must be a number or a string convertible to a number
-(see §3.4.2);
+(see §3.4.3);
otherwise, lua_tonumberx returns 0.
@@ -4735,23 +5715,23 @@
const void *lua_topointer (lua_State *L, int index);
-Converts the value at the given acceptable index to a generic
+Converts the value at the given index to a generic
C pointer (void*).
-The value can be a userdata, a table, a thread, or a function;
+The value can be a userdata, a table, a thread, a string, or a function;
otherwise, lua_topointer returns NULL.
Different objects will give different pointers.
There is no way to convert the pointer back to its original value.
-Typically this function is used only for debug information.
+Typically this function is used only for hashing and debug information.
lua_State *lua_tothread (lua_State *L, int index);
-Converts the value at the given acceptable index to a Lua thread
+Converts the value at the given index to a Lua thread
(represented as lua_State*).
This value must be a thread;
otherwise, the function returns NULL.
@@ -4775,55 +5755,15 @@
lua_Unsigned lua_tounsignedx (lua_State *L, int index, int *isnum);
-
-
-Converts the Lua value at the given acceptable index
-to the unsigned integral type lua_Unsigned.
-The Lua value must be a number or a string convertible to a number
-(see §3.4.2);
-otherwise, lua_tounsignedx returns 0.
-
-
-
-If the number is not an integer,
-it is truncated in some non-specified way.
-If the number is outside the range of representable values,
-it is normalized to the remainder of its division by
-one more than the maximum representable value.
-
-
-
-If isnum is not NULL,
-its referent is assigned a boolean value that
-indicates whether the operation succeeded.
-
-
-
-
-
-If the value at the given acceptable index is a full userdata,
-returns its block address.
+If the value at the given index is a full userdata,
+returns its memory-block address.
If the value is a light userdata,
-returns its pointer.
+returns its value (a pointer).
Otherwise, returns NULL.
@@ -4835,8 +5775,8 @@
-Returns the type of the value in the given acceptable index,
-or LUA_TNONE for a non-valid index.
+Returns the type of the value in the given valid index,
+or LUA_TNONE for a non-valid but acceptable index.
The types returned by lua_type are coded by the following constants
defined in lua.h:
LUA_TNIL,
@@ -4867,31 +5807,71 @@
-By default it is an unsigned int or an unsigned long,
-whichever can hold 32-bit values.
+Returns the pseudo-index that represents the i-th upvalue of
+the running function (see §4.2).
+i must be in the range [1,256].
typedef void (*lua_WarnFunction) (void *ud, const char *msg, int tocont);
+
+
+The type of warning functions, called by Lua to emit warnings.
+The first parameter is an opaque pointer
+set by lua_setwarnf.
+The second parameter is the warning message.
+The third parameter is a boolean that
+indicates whether the message is
+to be continued by the message in the next call.
+
+
+
+See warn for more details about warnings.
+
+
+
+
+
+
void lua_warning (lua_State *L, const char *msg, int tocont);
+
+
+Emits a warning with the given message.
+A message in a call with tocont true should be
+continued in another call to this function.
+
-Returns the address of the version number stored in the Lua core.
-When called with a valid lua_State,
-returns the address of the version used to create that state.
-When called with NULL,
-returns the address of the version running the call.
+See warn for more details about warnings.
@@ -4905,11 +5885,11 @@
The type of the writer function used by lua_dump.
-Every time it produces another piece of chunk,
-lua_dump calls the writer,
+Every time lua_dump produces another piece of chunk,
+it calls the writer,
passing along the buffer to be written (p),
its size (sz),
-and the data parameter supplied to lua_dump.
+and the ud parameter supplied to lua_dump.
This function is equivalent to lua_yieldk,
-but it has no continuation (see §4.7).
+but it has no continuation (see §4.5).
Therefore, when the thread resumes,
-it returns to the function that called
+it continues the function that called
the function calling lua_yield.
+To avoid surprises,
+this function should be called only in a tail call.
int lua_yieldk (lua_State *L, int nresults, int ctx, lua_CFunction k);
+[-?, +?, v]
+
int lua_yieldk (lua_State *L,
+ int nresults,
+ lua_KContext ctx,
+ lua_KFunction k);
-Yields a coroutine.
+Yields a coroutine (thread).
-This function should only be called as the
-return expression of a C function, as follows:
-
-
- return lua_yieldk (L, n, i, k);
-
-When a C function calls lua_yieldk in that way,
+When a C function calls lua_yieldk,
the running coroutine suspends its execution,
and the call to lua_resume that started this coroutine returns.
The parameter nresults is the number of values from the stack
-that are passed as results to lua_resume.
+that will be passed as results to lua_resume.
When the coroutine is resumed again,
Lua calls the given continuation function k to continue
-the execution of the C function that yielded (see §4.7).
+the execution of the C function that yielded (see §4.5).
This continuation function receives the same stack
from the previous function,
-with the results removed and
+with the n results removed and
replaced by the arguments passed to lua_resume.
Moreover,
-the continuation function may access the value ctx
-by calling lua_getctx.
+the continuation function receives the value ctx
+that was passed to lua_yieldk.
+
+
+
+Usually, this function does not return;
+when the coroutine eventually resumes,
+it continues executing the continuation function.
+However, there is one special case,
+which is when this function is called
+from inside a line or a count hook (see §4.7).
+In that case, lua_yieldk should be called with no continuation
+(probably in the form of lua_yield) and no results,
+and the hook should return immediately after the call.
+Lua will yield and,
+when the coroutine resumes again,
+it will continue the normal execution
+of the (Lua) function that triggered the hook.
+
+
+
+This function can raise an error if it is called from a thread
+with a pending C call with no continuation function
+(what is called a C-call boundary),
+or it is called from a thread that is not running inside a resume
+(typically the main thread).
@@ -4993,7 +5996,7 @@
unsigned char nparams; /* (u) number of parameters */
char isvararg; /* (u) */
char istailcall; /* (t) */
+ unsigned short ftransfer; /* (r) index of first value transferred */
+ unsigned short ntransfer; /* (r) number of transferred values */
char short_src[LUA_IDSIZE]; /* (S) */
/* private part */
other fields
@@ -5030,7 +6036,10 @@
lua_getstack fills only the private part
of this structure, for later use.
To fill the other fields of lua_Debug with useful information,
-call lua_getinfo.
+you must call lua_getinfo with an appropriate parameter.
+(Specifically, to get a field,
+you must add the letter between parentheses in the field's comment
+to the parameter what of lua_getinfo.)
it means that the function was defined in a file where
the file name follows the '@'.
If source starts with a '=',
-the remainder of its contents describe the source in a user-dependent manner.
+the remainder of its contents describes the source in a user-dependent manner.
Otherwise,
the function was defined in a string where
source is that string.
+
srclen:
+The length of the string source.
+
+
short_src:
a "printable" version of source, to be used in error messages.
nparams:
-the number of fixed parameters of the function
+the number of parameters of the function
(always 0 for C functions).
isvararg:
-true if the function is a vararg function
+true if the function is a variadic function
(always true for C functions).
+
ftransfer:
+the index in the stack of the first value being "transferred",
+that is, parameters in a call or return values in a return.
+(The other values are in consecutive indices.)
+Using this index, you can access and modify these values
+through lua_getlocal and lua_setlocal.
+This field is only meaningful during a
+call hook, denoting the first parameter,
+or a return hook, denoting the first value being returned.
+(For call hooks, this value is always 1.)
+
+
+
ntransfer:
+The number of values being transferred (see previous item).
+(For calls of Lua functions,
+this value is always equal to nparams.)
+
-To get information about a function you push it onto the stack
+To get information about a function, you push it onto the stack
and start the what string with the character '>'.
(In that case,
lua_getinfo pops the function from the top of the stack.)
@@ -5185,11 +6216,25 @@
Each character in the string what
selects some fields of the structure ar to be filled or
-a value to be pushed on the stack:
+a value to be pushed on the stack.
+(These characters are also documented in the declaration of
+the structure lua_Debug,
+between parentheses in the comments following each field.)
-
'n': fills in the field name and namewhat;
+
'f':
+pushes onto the stack the function that is
+running at the given level;
+
'f':
-pushes onto the stack the function that is
-running at the given level;
-
-
'L':
-pushes onto the stack a table whose indices are the
-numbers of the lines that are valid on the function.
-(A valid line is a line with some associated code,
-that is, a line where you can put a break point.
-Non-valid lines include empty lines and comments.)
+pushes onto the stack a table whose indices are
+the lines on the function with some associated code,
+that is, the lines where you can put a break point.
+(Lines with no code include empty lines and comments.)
+If this option is given together with option 'f',
+its table is pushed after the function.
+This is the only option that can raise a memory error.
-This function returns 0 on error
-(for instance, an invalid option in what).
+This function returns 0 to signal an invalid option in what;
+even then the valid options are handled correctly.
@@ -5232,11 +6271,11 @@
const char *lua_getlocal (lua_State *L, lua_Debug *ar, int n);
+
const char *lua_getlocal (lua_State *L, const lua_Debug *ar, int n);
-Gets information about a local variable of
-a given activation record or a given function.
+Gets information about a local variable or a temporary value
+of a given activation record or a given function.
-In the second case, ar should be NULL and the function
-to be inspected must be at the top of the stack.
+In the second case, ar must be NULL and the function
+to be inspected must be on the top of the stack.
In this case, only parameters of Lua functions are visible
(as there is no information about what variables are active)
and no values are pushed onto the stack.
@@ -5285,10 +6324,10 @@
of the function executing at a given level.
Level 0 is the current running function,
whereas level n+1 is the function that has called level n
-(except for tail calls, which do not count on the stack).
-When there are no errors, lua_getstack returns 1;
-when called with a level greater than the stack depth,
-it returns 0.
+(except for tail calls, which do not count in the stack).
+When called with a level greater than the stack depth,
+lua_getstack returns 0;
+otherwise it returns 1.
@@ -5299,24 +6338,16 @@
const char *lua_getupvalue (lua_State *L, int funcindex, int n);
-Gets information about a closure's upvalue.
-(For Lua functions,
-upvalues are the external local variables that the function uses,
-and that are consequently included in its closure.)
-lua_getupvalue gets the index n of an upvalue,
-pushes the upvalue's value onto the stack,
+Gets information about the n-th upvalue
+of the closure at index funcindex.
+It pushes the upvalue's value onto the stack
and returns its name.
-funcindex points to the closure in the stack.
-(Upvalues have no particular order,
-as they are active through the whole function.
-So, they are numbered in an arbitrary order.)
+Returns NULL (and pushes nothing)
+when the index n is greater than the number of upvalues.
-Returns NULL (and pushes nothing)
-when the index is greater than the number of upvalues.
-For C functions, this function uses the empty string ""
-as a name for all upvalues.
+See debug.getupvalue for more information about upvalues.
@@ -5361,10 +6392,10 @@
Hook functions can yield under the following conditions:
-Only count and line events can yield
-and they cannot yield any value;
-to yield a hook function must finish its execution
-calling lua_yield with nresults equal to zero.
+Only count and line events can yield;
+to yield, a hook function must finish its execution
+calling lua_yield with nresults equal to zero
+(that is, with no values).
@@ -5372,7 +6403,7 @@
Argument f is the hook function.
mask specifies on which events the hook will be called:
-it is formed by a bitwise or of the constants
+it is formed by a bitwise OR of the constants
LUA_MASKCALL,
LUA_MASKRET,
LUA_MASKLINE,
@@ -5393,31 +6424,28 @@
The call hook: is called when the interpreter calls a function.
-The hook is called just after Lua enters the new function,
-before the function gets its arguments.
+The hook is called just after Lua enters the new function.
The return hook: is called when the interpreter returns from a function.
The hook is called just before Lua leaves the function.
-There is no standard way to access the values
-to be returned by the function.
The line hook: is called when the interpreter is about to
start the execution of a new line of code,
or when it jumps back in the code (even to the same line).
-(This event only happens while Lua is executing a Lua function.)
+This event only happens while Lua is executing a Lua function.
The count hook: is called after the interpreter executes every
count instructions.
-(This event only happens while Lua is executing a Lua function.)
+This event only happens while Lua is executing a Lua function.
-A hook is disabled by setting mask to zero.
+Hooks are disabled by setting mask to zero.
@@ -5425,13 +6453,11 @@
const char *lua_setlocal (lua_State *L, lua_Debug *ar, int n);
+
const char *lua_setlocal (lua_State *L, const lua_Debug *ar, int n);
Sets the value of a local variable of a given activation record.
-Parameters ar and n are as in lua_getlocal
-(see lua_getlocal).
-lua_setlocal assigns the value at the top of the stack
+It assigns the value on the top of the stack
to the variable and returns its name.
It also pops the value from the stack.
@@ -5442,6 +6468,10 @@
Sets the value of a closure's upvalue.
-It assigns the value at the top of the stack
+It assigns the value on the top of the stack
to the upvalue and returns its name.
It also pops the value from the stack.
-Parameters funcindex and n are as in the lua_getupvalue
-(see lua_getupvalue).
Returns NULL (and pops nothing)
-when the index is greater than the number of upvalues.
+when the index n is greater than the number of upvalues.
+
+
+
+Parameters funcindex and n are as in
+the function lua_getupvalue.
@@ -5471,11 +6504,8 @@
void *lua_upvalueid (lua_State *L, int funcindex, int n);
-Returns an unique identifier for the upvalue numbered n
+Returns a unique identifier for the upvalue numbered n
from the closure at index funcindex.
-Parameters funcindex and n are as in the lua_getupvalue
-(see lua_getupvalue)
-(but n cannot be greater than the number of upvalues).
Functions called luaL_check*
-always throw an error if the check is not satisfied.
+always raise an error if the check is not satisfied.
+
+
@@ -5561,7 +6601,7 @@
-Adds to the buffer B (see luaL_Buffer)
+Adds to the buffer B
a string of length n previously copied to the
buffer area (see luaL_prepbuffer).
@@ -5600,25 +6654,24 @@
-Adds the value at the top of the stack
+Adds the value on the top of the stack
to the buffer B
(see luaL_Buffer).
Pops the value.
@@ -5642,7 +6695,7 @@
Checks whether cond is true.
-If not, raises an error with a standard message.
+If it is not, raises an error with a standard message (see luaL_argerror).
@@ -5653,14 +6706,31 @@
int luaL_argerror (lua_State *L, int arg, const char *extramsg);
-Raises an error with a standard message
-that includes extramsg as a comment.
+Raises an error reporting a problem with argument arg
+of the C function that called it,
+using a standard message
+that includes extramsg as a comment:
+
+
void luaL_argexpected (lua_State *L,
+ int cond,
+ int arg,
+ const char *tname);
+
-This function never returns,
-but it is an idiom to use it in C functions
-as return luaL_argerror(args).
+Checks whether cond is true.
+If it is not, raises an error about the type of the argument arg
+with a standard message (see luaL_typeerror).
@@ -5696,7 +6766,7 @@
-If you know beforehand the total size of the resulting string,
+If you know beforehand the maximum size of the resulting string,
you can use the buffer like this:
Then initialize it and preallocate a space of
size sz with a call luaL_buffinitsize(L, &b, sz).
-
Then copy the string into that space.
+
Then produce the string into that space.
Finish by calling luaL_pushresultsize(&b, sz),
where sz is the total size of the resulting string
-copied into that space.
+copied into that space (which may be less than or
+equal to the preallocated size).
the stack is at the same level
it was immediately after the previous buffer operation.
(The only exception to this rule is luaL_addvalue.)
-After calling luaL_pushresult the stack is back to its
-level when the buffer was initialized,
+After calling luaL_pushresult,
+the stack is back to its level when the buffer was initialized,
plus the final string on its top.
-
+Returns the address of the current content of buffer B
+(see luaL_Buffer).
+Note that any addition to the buffer may invalidate this address.
+
+
+
+
+
+
-Initializes a buffer B.
+Initializes a buffer B
+(see luaL_Buffer).
This function does not allocate any space;
-the buffer must be declared as a variable
+the buffer must be declared as a variable.
+
+
+
+
+
+
In this case this function returns true and pushes onto the
stack the value returned by the call.
If there is no metatable or no metamethod,
-this function returns false (without pushing any value on the stack).
+this function returns false without pushing any value on the stack.
@@ -5795,37 +6904,14 @@
-Checks whether the function argument arg is a number
-and returns this number cast to a long.
+Checks whether the function argument arg is an integer
+(or can be converted to an integer)
+and returns this integer.
@@ -5838,7 +6924,7 @@
Checks whether the function argument arg is a string
and returns this string;
-if l is not NULL fills *l
+if l is not NULL fills its referent
with the string's length.
@@ -5856,7 +6942,7 @@
Checks whether the function argument arg is a number
-and returns this number.
+and returns this number converted to a lua_Number.
@@ -5943,42 +7029,26 @@
Checks whether the function argument arg is a userdata
of the type tname (see luaL_newmetatable) and
-returns the userdata address (see lua_touserdata).
-
-
-
-
-
-
lua_Unsigned luaL_checkunsigned (lua_State *L, int arg);
-
-
-Checks whether the function argument arg is a number
-and returns this number cast to a lua_Unsigned.
+returns the userdata's memory-block address (see lua_touserdata).
-Checks whether the core running the call,
-the core that created the Lua state,
-and the code making the call are all using the same version of Lua.
-Also checks whether the core running the call
-and the core that created the Lua state
-are using the same address space.
+Checks whether the code making the call and the Lua library being called
+are using the same version of Lua and the same numeric types.
-It returns false if there are no errors
-or true in case of errors.
+It returns 0 (LUA_OK) if there are no errors,
+or 1 in case of errors.
@@ -6006,8 +7076,8 @@
-It returns false if there are no errors
-or true in case of errors.
+It returns 0 (LUA_OK) if there are no errors,
+or 1 in case of errors.
@@ -6037,7 +7107,7 @@
int luaL_getmetafield (lua_State *L, int obj, const char *e);
Pushes onto the stack the field e from the metatable
-of the object at index obj.
+of the object at index obj and returns the type of the pushed value.
If the object does not have a metatable,
or if the metatable does not have this field,
-returns false and pushes nothing.
+pushes nothing and returns LUA_TNIL.
int luaL_getmetatable (lua_State *L, const char *tname);
-Pushes onto the stack the metatable associated with name tname
-in the registry (see luaL_newmetatable).
+Pushes onto the stack the metatable associated with the name tname
+in the registry (see luaL_newmetatable),
+or nil if there is no metatable associated with that name.
+Returns the type of the pushed value.
@@ -6095,7 +7167,7 @@
Ensures that the value t[fname],
-where t is the value at the valid index idx,
+where t is the value at index idx,
is a table,
and pushes that table onto the stack.
Returns true if it finds a previous table there
@@ -6106,15 +7178,15 @@
-Creates a copy of string s by replacing
-any occurrence of the string p
+Creates a copy of string s,
+replacing any occurrence of the string p
with the string r.
Pushes the resulting string on the stack and returns it.
@@ -6124,14 +7196,14 @@
-Returns the "length" of the value at the given acceptable index
+Returns the "length" of the value at the given index
as a number;
-it is equivalent to the '#' operator in Lua (see §3.4.6).
-Raises an error if the result of the operation is not a number.
-(This case only can happen through metamethods.)
+it is equivalent to the '#' operator in Lua (see §3.4.7).
+Raises an error if the result of the operation is not an integer.
+(This case can only happen through metamethods.)
@@ -6169,14 +7241,14 @@
This function returns the same results as lua_load.
name is the chunk name,
used for debug information and error messages.
-The string mode works as in function lua_load.
+The string mode works as in the function lua_load.
-The string mode works as in function lua_load.
+The string mode works as in the function lua_load.
-This function returns the same results as lua_load,
-but it has an extra error code LUA_ERRFILE
-if it cannot open/read the file or the file has a wrong mode.
+This function returns the same results as lua_load
+or LUA_ERRFILE for file-related errors.
returns 0.
Otherwise,
creates a new table to be used as a metatable for userdata,
-adds it to the registry with key tname,
+adds to this new table the pair __name = tname,
+adds to the registry the pair [tname] = new table,
and returns 1.
-In both cases pushes onto the stack the final value associated
+In both cases,
+the function pushes onto the stack the final value associated
with tname in the registry.
@@ -6305,10 +7384,9 @@
Creates a new Lua state.
It calls lua_newstate with an
-allocator based on the standard C realloc function
-and then sets a panic function (see §4.6) that prints
-an error message to the standard error output in case of fatal
-errors.
+allocator based on the ISO C allocation functions
+and then sets a warning function and a panic function (see §4.4)
+that print messages to the standard error output.
-If the function argument arg is a number,
-returns this number cast to an int.
-If this argument is absent or is nil,
-returns d.
-Otherwise, raises an error.
+This macro is defined as follows:
+
+
+In words, if the argument arg is nil or absent,
+the macro results in the default dflt.
+Otherwise, it results in the result of calling func
+with the state L and the argument index arg as
+arguments.
+Note that it evaluates the expression dflt only if needed.
@@ -6352,23 +7436,9 @@
-If the function argument arg is a number,
-returns this number cast to a lua_Integer.
-If this argument is absent or is nil,
-returns d.
-Otherwise, raises an error.
-
-
-
-
-
-
long luaL_optlong (lua_State *L, int arg, long d);
-
-
-If the function argument arg is a number,
-returns this number cast to a long.
+If the function argument arg is an integer
+(or it is convertible to an integer),
+returns this integer.
If this argument is absent or is nil,
returns d.
Otherwise, raises an error.
@@ -6394,7 +7464,15 @@
If l is not NULL,
-fills the position *l with the result's length.
+fills its referent with the result's length.
+If the result is NULL
+(only possible when returning d and d == NULL),
+its length is considered zero.
+
+
+
+This function uses lua_tolstring to get its result,
+so all conversions and caveats of that function apply here.
@@ -6406,7 +7484,7 @@
If the function argument arg is a number,
-returns this number.
+returns this number as a lua_Number.
If this argument is absent or is nil,
returns d.
Otherwise, raises an error.
@@ -6432,25 +7510,8 @@
lua_Unsigned luaL_optunsigned (lua_State *L,
- int arg,
- lua_Unsigned u);
-
-
-If the function argument arg is a number,
-returns this number cast to a lua_Unsigned.
-If this argument is absent or is nil,
-returns u.
-Otherwise, raises an error.
-
-
-
-
-
Creates and returns a reference,
in the table at index t,
-for the object at the top of the stack (and pops the object).
+for the object on the top of the stack (and pops the object).
A reference is a unique integer key.
-As long as you do not manually add integer keys into table t,
+As long as you do not manually add integer keys into the table t,
luaL_ref ensures the uniqueness of the key it returns.
-You can retrieve an object referred by reference r
+You can retrieve an object referred by the reference r
by calling lua_rawgeti(L, t, r).
-Function luaL_unref frees a reference and its associated object.
+The function luaL_unref frees a reference.
-If the object at the top of the stack is nil,
+If the object on the top of the stack is nil,
luaL_ref returns the constant LUA_REFNIL.
The constant LUA_NOREF is guaranteed to be different
from any reference returned by luaL_ref.
@@ -6540,7 +7612,7 @@
luaL_setfuncs.
name is the function name and func is a pointer to
the function.
-Any array of luaL_Reg must end with an sentinel entry
+Any array of luaL_Reg must end with a sentinel entry
in which both name and func are NULL.
@@ -6553,25 +7625,26 @@
-Calls function openf with string modname as an argument
-and sets the call result in package.loaded[modname],
+If package.loaded[modname] is not true,
+calls the function openf with the string modname as an argument
+and sets the call result to package.loaded[modname],
as if that function has been called through require.
If glb is true,
-also stores the result into global modname.
+also stores the module into the global modname.
-Leaves a copy of that result on the stack.
+Leaves a copy of the module on the stack.
When nup is not zero,
-all functions are created sharing nup upvalues,
-which must be previously pushed on the stack
+all functions are created with nup upvalues,
+initialized with copies of the nup values
+previously pushed on the stack
on top of the library table.
These values are popped from the stack after the registration.
+
+A function with a NULL value represents a placeholder,
+which is filled with false.
+
+
@@ -6596,7 +7675,7 @@
-Sets the metatable of the object at the top of the stack
+Sets the metatable of the object on the top of the stack
as the metatable associated with name tname
in the registry (see luaL_newmetatable).
@@ -6604,14 +7683,52 @@
+The standard representation for file handles
+used by the standard I/O library.
+
+
+
+A file handle is implemented as a full userdata,
+with a metatable called LUA_FILEHANDLE
+(where LUA_FILEHANDLE is a macro with the actual metatable's name).
+The metatable is created by the I/O library
+(see luaL_newmetatable).
+
+
+
+This userdata must start with the structure luaL_Stream;
+it can contain other data after this initial structure.
+The field f points to the corresponding C stream
+(or it can be NULL to indicate an incompletely created handle).
+The field closef points to a Lua function
+that will be called to close the stream
+when the handle is closed or collected;
+this function receives the file handle as its sole argument and
+must return either a true value, in case of success,
+or a false value plus an error message, in case of error.
+Once Lua calls this field,
+it changes the field value to NULL
+to signal that the handle is closed.
+
+
+
+
+
void *luaL_testudata (lua_State *L, int arg, const char *tname);
This function works like luaL_checkudata,
except that, when the test fails,
-it returns NULL instead of throwing an error.
+it returns NULL instead of raising an error.
@@ -6622,16 +7739,16 @@
const char *luaL_tolstring (lua_State *L, int idx, size_t *len);
-Converts any Lua value at the given acceptable index to a C string
+Converts any Lua value at the given index to a C string
in a reasonable format.
The resulting string is pushed onto the stack and also
-returned by the function.
+returned by the function (see §4.1.3).
If len is not NULL,
the function also sets *len with the string length.
-If the value has a metatable with a "__tostring" field,
+If the value has a metatable with a __tostring field,
then luaL_tolstring calls the corresponding metamethod
with the value as argument,
and uses the result of the call as its result.
@@ -6641,13 +7758,13 @@
Creates and pushes a traceback of the stack L1.
-If msg is not NULL it is appended
+If msg is not NULL, it is appended
at the beginning of the traceback.
The level parameter tells at which level
to start the traceback.
@@ -6656,6 +7773,21 @@
int luaL_typeerror (lua_State *L, int arg, const char *tname);
+
+
+Raises a type error for the argument arg
+of the C function that called it,
+using a standard message;
+tname is a "name" for the expected type.
+This function never returns.
+
+
+
+
+
-Releases reference ref from the table at index t
+Releases the reference ref from the table at index t
(see luaL_ref).
The entry is removed from the table,
so that the referred object can be collected.
@@ -6688,7 +7820,7 @@
The standard Lua libraries provide useful functions
-that are implemented directly through the C API.
+that are implemented in C through the C API.
Some of these functions provide essential services to the language
(e.g., type and getmetatable);
-others provide access to "outside" services (e.g., I/O);
+others provide access to outside services (e.g., I/O);
and others could be implemented in Lua itself,
-but are quite useful or have critical performance requirements that
+but that for different reasons
deserve an implementation in C (e.g., table.sort).
All libraries are implemented through the official C API
and are provided as separate C modules.
+Unless otherwise noted,
+these library functions do not adjust its number of arguments
+to its expected parameters.
+For instance, a function documented as foo(arg)
+should not be called without an argument.
+
+
+
+The notation fail means a false value representing
+some kind of failure.
+(Currently, fail is equal to nil,
+but that may change in future versions.
+The recommendation is to always test the success of these functions
+with (not status), instead of (status == nil).)
+
+
+
Currently, Lua has the following standard libraries:
+Raises an error if
the value of its argument v is false (i.e., nil or false);
otherwise, returns all its arguments.
-message is an error message;
-when absent, it defaults to "assertion failed!"
+In case of error,
+message is the error object;
+when absent, it defaults to "assertion failed!"
@@ -6811,91 +7968,88 @@
"collect":
-performs a full garbage-collection cycle.
+Performs a full garbage-collection cycle.
This is the default option.
"stop":
-stops automatic execution of the garbage collector.
+Stops automatic execution of the garbage collector.
The collector will run only when explicitly invoked,
until a call to restart it.
"restart":
-restarts automatic execution of the garbage collector.
+Restarts automatic execution of the garbage collector.
"count":
-returns the total memory in use by Lua (in Kbytes) and
-a second value with the total memory in bytes modulo 1024.
-The first value has a fractional part,
-so the following equality is always true:
-
-
- k, b = collectgarbage("count")
- assert(k*1024 == math.floor(k)*1024 + b)
-
-(The second result is useful when Lua is compiled
-with a non floating-point type for numbers.)
+Returns the total memory in use by Lua in Kbytes.
+The value has a fractional part,
+so that it multiplied by 1024
+gives the exact number of bytes in use by Lua.
"step":
-performs a garbage-collection step.
-The step "size" is controlled by arg
-(larger values mean more steps) in a non-specified way.
-If you want to control the step size
-you must experimentally tune the value of arg.
+Performs a garbage-collection step.
+The step "size" is controlled by arg.
+With a zero value,
+the collector will perform one basic (indivisible) step.
+For non-zero values,
+the collector will perform as if that amount of memory
+(in Kbytes) had been allocated by Lua.
Returns true if the step finished a collection cycle.
-
"setpause":
-sets arg as the new value for the pause of
-the collector (see §2.5).
-Returns the previous value for pause.
-
-
-
"setstepmul":
-sets arg as the new value for the step multiplier of
-the collector (see §2.5).
-Returns the previous value for step.
-
-
"isrunning":
-returns a boolean that tells whether the collector is running
+Returns a boolean that tells whether the collector is running
(i.e., not stopped).
+
"incremental":
+Change the collector mode to incremental.
+This option can be followed by three numbers:
+the garbage-collector pause,
+the step multiplier,
+and the step size (see §2.5.1).
+A zero means to not change that value.
+
+
"generational":
-changes the collector to generational mode.
-This is an experimental feature (see §2.5).
+Change the collector mode to generational.
+This option can be followed by two numbers:
+the garbage-collector minor multiplier
+and the major multiplier (see §2.5.2).
+A zero means to not change that value.
-
"incremental":
-changes the collector to incremental mode.
-This is the default mode.
-
+
+See §2.5 for more details about garbage collection
+and some of these options.
+
+
+
+This function should not be called by a finalizer.
-
-Opens the named file and executes its contents as a Lua chunk.
+Opens the named file and executes its content as a Lua chunk.
When called without arguments,
-dofile executes the contents of the standard input (stdin).
+dofile executes the content of the standard input (stdin).
Returns all values returned by the chunk.
In case of errors, dofile propagates the error
-to its caller (that is, dofile does not run in protected mode).
+to its caller.
+(That is, dofile does not run in protected mode.)
-Terminates the last protected function called
-and returns message as the error message.
-Function error never returns.
+Raises an error (see §2.3) with message as the error object.
+This function never returns.
holds the global environment (see §2.2).
Lua itself does not use this variable;
changing its value does not affect any environment,
-nor vice-versa.
+nor vice versa.
@@ -6930,7 +8084,7 @@
If object does not have a metatable, returns nil.
Otherwise,
-if the object's metatable has a "__metatable" field,
+if the object's metatable has a __metatable field,
returns the associated value.
Otherwise, returns the metatable of the given object.
@@ -6942,27 +8096,21 @@
-If t has a metamethod __ipairs,
-calls it with t as argument and returns the first three
-results from the call.
-
-
-
-Otherwise,
-returns three values: an iterator function, the table t, and 0,
+Returns three values (an iterator function, the table t, and 0)
so that the construction
for i,v in ipairs(t) do body end
-will iterate over the pairs (1,t[1]), (2,t[2]), ...,
-up to the first integer key absent from the table.
+will iterate over the key–value pairs
+(1,t[1]), (2,t[2]), ...,
+up to the first absent index.
-If ld is a string, the chunk is this string.
-If ld is a function,
+If chunk is a string, the chunk is this string.
+If chunk is a function,
load calls it repeatedly to get the chunk pieces.
-Each call to ld must return a string that concatenates
+Each call to chunk must return a string that concatenates
with previous results.
A return of an empty string, nil, or no value signals the end of the chunk.
If there are no syntactic errors,
-returns the compiled chunk as a function;
-otherwise, returns nil plus the error message.
+load returns the compiled chunk as a function;
+otherwise, it returns fail plus the error message.
-If the resulting function has upvalues,
-the first upvalue is set to the value of the
-global environment or to env,
-if that parameter is given.
-When loading main chunks,
-the first upvalue will be the _ENV variable (see §2.2).
+When you load a main chunk,
+the resulting function will always have exactly one upvalue,
+the _ENV variable (see §2.2).
+However,
+when you load a binary chunk created from a function (see string.dump),
+the resulting function can have an arbitrary number of upvalues,
+and there is no guarantee that its first upvalue will be
+the _ENV variable.
+(A non-main function may not even have an _ENV upvalue.)
+
+
+
+Regardless, if the resulting function has any upvalues,
+its first upvalue is set to the value of env,
+if that parameter is given,
+or to the value of the global environment.
+Other upvalues are initialized with nil.
+All upvalues are fresh, that is,
+they are not shared with any other function.
-source is used as the source of the chunk for error messages
-and debug information (see §4.9).
+chunkname is used as the name of the chunk for error messages
+and debug information (see §4.7).
When absent,
-it defaults to ld, if ld is a string,
+it defaults to chunk, if chunk is a string,
or to "=(load)" otherwise.
@@ -7010,6 +8171,14 @@
+It is safe to load malformed binary chunks;
+load signals an appropriate error.
+However,
+Lua does not check the consistency of the code inside binary chunks;
+running maliciously crafted bytecode can crash the interpreter.
+
+
Allows a program to traverse all fields of a table.
Its first argument is a table and its second argument
is an index in this table.
-next returns the next index of the table
+A call to next returns the next index of the table
and its associated value.
When called with nil as its second argument,
next returns an initial index
@@ -7049,16 +8218,15 @@
The order in which the indices are enumerated is not specified,
even for numeric indices.
-(To traverse a table in numeric order,
+(To traverse a table in numerical order,
use a numerical for.)
-The behavior of next is undefined if,
-during the traversal,
-you assign any value to a non-existent field in the table.
+You should not assign any value to a non-existent field in a table
+during its traversal.
You may however modify existing fields.
-In particular, you may clear existing fields.
+In particular, you may set existing fields to nil.
@@ -7096,16 +8264,17 @@
-Calls function f with
+Calls the function f with
the given arguments in protected mode.
This means that any error inside f is not propagated;
instead, pcall catches the error
and returns a status code.
Its first result is the status code (a boolean),
-which is true if the call succeeds without errors.
+which is true if the call succeeds without errors.
In such case, pcall also returns all results from the call,
after this first result.
-In case of any error, pcall returns false plus the error message.
+In case of any error, pcall returns false plus the error object.
+Note that errors caught by pcall do not call a message handler.
@@ -7114,8 +8283,12 @@
Receives any number of arguments
and prints their values to stdout,
-using the tostring function to convert each argument to a string.
-print is not intended for formatted output,
+converting each argument to a string
+following the same rules of tostring.
+
+
+
+The function print is not intended for formatted output,
but only as a quick way to show a value,
for instance for debugging.
For complete control over the output,
@@ -7127,7 +8300,7 @@
Gets the real value of table[index],
-without invoking any metamethod.
+without using the __index metavalue.
table must be a table;
index may be any value.
@@ -7147,8 +8320,8 @@
Returns the length of the object v,
which must be a table or a string,
-without invoking any metamethod.
-Returns an integer number.
+without invoking the __len metamethod.
+Returns an integer.
@@ -7156,7 +8329,7 @@
Sets the real value of table[index] to value,
-without invoking any metamethod.
+without using the __newindex metavalue.
table must be a table,
index any value different from nil and NaN,
and value any Lua value.
@@ -7188,10 +8361,9 @@
Sets the metatable for the given table.
-(You cannot change the metatable of other types from Lua, only from C.)
If metatable is nil,
removes the metatable of the given table.
-If the original metatable has a "__metatable" field,
+If the original metatable has a __metatable field,
raises an error.
@@ -7199,6 +8371,11 @@
When called with no base,
tonumber tries to convert its argument to a number.
If the argument is already a number or
-a string convertible to a number (see §3.4.2),
+a string convertible to a number,
then tonumber returns this number;
-otherwise, it returns nil.
+otherwise, it returns fail.
+
+
+
+The conversion of strings can result in integers or floats,
+according to the lexical conventions of Lua (see §3.1).
+The string may have leading and trailing spaces and a sign.
When called with base,
-then e should be a string to be interpreted as
+then e must be a string to be interpreted as
an integer numeral in that base.
The base may be any integer between 2 and 36, inclusive.
In bases above 10, the letter 'A' (in either upper or lower case)
represents 10, 'B' represents 11, and so forth,
with 'Z' representing 35.
If the string e is not a valid numeral in the given base,
-the function returns nil.
+the function returns fail.
Receives a value of any type and
-converts it to a string in a reasonable format.
-(For complete control of how numbers are converted,
-use string.format.)
+converts it to a string in a human-readable format.
-If the metatable of v has a "__tostring" field,
+If the metatable of v has a __tostring field,
then tostring calls the corresponding value
with v as argument,
and uses the result of the call as its result.
+Otherwise, if the metatable of v has a __name field
+with a string value,
+tostring may use that string in its final result.
+
+
+
+For complete control of how numbers are converted,
+use string.format.
Returns the type of its only argument, coded as a string.
The possible results of this function are
"nil" (a string, not the value nil),
@@ -7263,9 +8458,35 @@
A global variable (not a function) that
-holds a string containing the current interpreter version.
-The current contents of this variable is "Lua 5.2".
+holds a string containing the running Lua version.
+The current value of this variable is "Lua 5.4".
+
+
+
+
+
+Emits a warning with a message composed by the concatenation
+of all its arguments (which should be strings).
+
+
+
+By convention,
+a one-piece message starting with '@'
+is intended to be a control message,
+which is a message to the warning system itself.
+In particular, the standard warning function in Lua
+recognizes the control messages "@off",
+to stop the emission of warnings,
+and "@on", to (re)start the emission;
+it ignores unknown control messages.
@@ -7287,24 +8508,59 @@
-The operations related to coroutines comprise a sub-library of
-the basic library and come inside the table coroutine.
+This library comprises the operations to manipulate coroutines,
+which come inside the table coroutine.
See §2.6 for a general description of coroutines.
+
+Closes coroutine co,
+that is,
+closes all its pending to-be-closed variables
+and puts the coroutine in a dead state.
+The given coroutine must be dead or suspended.
+In case of error
+(either the original error that stopped the coroutine or
+errors in closing methods),
+returns false plus the error object;
+otherwise returns true.
+
+
+
+
If the coroutine runs without any errors,
resume returns true plus any values passed to yield
-(if the coroutine yields) or any values returned by the body function
-(if the coroutine terminates).
+(when the coroutine yields) or any values returned by the body function
+(when the coroutine terminates).
If there is any error,
resume returns false plus the error message.
@@ -7338,7 +8594,7 @@
Returns the running coroutine plus a boolean,
-true when the running coroutine is the main one.
+true when the running coroutine is the main one.
@@ -7348,9 +8604,10 @@
-Returns the status of coroutine co, as a string:
+Returns the status of the coroutine co, as a string:
"running",
-if the coroutine is running (that is, it called status);
+if the coroutine is running
+(that is, it is the one that called status);
"suspended", if the coroutine is suspended in a call to yield,
or if it has not started running yet;
"normal" if the coroutine is active but not running
@@ -7366,14 +8623,15 @@
-Creates a new coroutine, with body f.
-f must be a Lua function.
+Creates a new coroutine, with body f;
+f must be a function.
Returns a function that resumes the coroutine each time it is called.
-Any arguments passed to the function behave as the
+Any arguments passed to this function behave as the
extra arguments to resume.
-Returns the same values returned by resume,
+The function returns the same values returned by resume,
except the first boolean.
-In case of error, propagates the error.
+In case of error,
+the function closes the coroutine and propagates the error.
@@ -7399,7 +8657,7 @@
facilities for loading modules in Lua.
It exports one function directly in the global environment:
require.
-Everything else is exported in a table package.
+Everything else is exported in the table package.
to determine whether modname is already loaded.
If it is, then require returns the value stored
at package.loaded[modname].
+(The absence of a second result in this case
+signals that this call did not have to load the module.)
Otherwise, it tries to find a loader for the module.
To find a loader,
-require is guided by the package.searchers sequence.
-By changing this sequence,
+require is guided by the table package.searchers.
+Each item in this table is a search function,
+that searches for the module in a particular way.
+By changing this table,
we can change how require looks for a module.
The following explanation is based on the default configuration
for package.searchers.
@@ -7427,7 +8689,7 @@
First require queries package.preload[modname].
If it has a value,
-this value (which should be a function) is the loader.
+this value (which must be a function) is the loader.
Otherwise require searches for a Lua loader using the
path stored in package.path.
If that also fails, it searches for a C loader using the
@@ -7439,9 +8701,14 @@
Once a loader is found,
require calls the loader with two arguments:
-modname and an extra value dependent on how it got the loader.
-(If the loader came from a file,
-this extra value is the file name.)
+modname and an extra value,
+a loader data,
+also returned by the searcher.
+The loader data can be any value useful to the module;
+for the default searchers,
+it indicates where the loader was found.
+(For instance, if the loader came from a file,
+this extra value is the file path.)
If the loader returns any non-nil value,
require assigns the returned value to package.loaded[modname].
If the loader does not return a non-nil value and
@@ -7449,6 +8716,9 @@
then require assigns true to this entry.
In any case, require returns the
final value of package.loaded[modname].
+Besides that value, require also returns as a second result
+the loader data returned by the searcher,
+which indicates how require found the module.
-The path used by require to search for a C loader.
+A string with the path used by require
+to search for a C loader.
Lua initializes the C path package.cpath in the same way
it initializes the Lua path package.path,
-using the environment variable LUA_CPATH_5_2
-or the environment variable LUA_CPATH
+using the environment variable LUA_CPATH_5_4,
+or the environment variable LUA_CPATH,
or a default path defined in luaconf.h.
This variable is only a reference to the real table;
assignments to this variable do not change the
table used by require.
+The real table is stored in the C registry (see §4.3),
+indexed by the key LUA_LOADED_TABLE, a string.
@@ -7546,7 +8818,8 @@
Otherwise,
it looks for a function funcname inside the library
and returns this function as a C function.
-(So, funcname must follow the prototype lua_CFunction).
+So, funcname must follow the lua_CFunction prototype
+(see lua_CFunction).
-This function is not supported by Standard C.
+This functionality is not supported by ISO C.
As such, it is only available on some platforms
(Windows, Linux, Mac OS X, Solaris, BSD,
plus other Unix systems that support the dlfcn standard).
+
+This function is inherently insecure,
+as it allows Lua to call any function in any readable dynamic
+library in the system.
+(Lua calls any function assuming the function
+has a proper prototype and respects a proper protocol
+(see lua_CFunction).
+Therefore,
+calling an arbitrary function in an arbitrary dynamic library
+more often than not results in an access violation.)
+
+
-The path used by require to search for a Lua loader.
+A string with the path used by require
+to search for a Lua loader.
At start-up, Lua initializes this variable with
-the value of the environment variable LUA_PATH_5_2 or
+the value of the environment variable LUA_PATH_5_4 or
the environment variable LUA_PATH or
with a default path defined in luaconf.h,
if those environment variables are not defined.
-Any ";;" in the value of the environment variable
+A ";;" in the value of the environment variable
is replaced by the default path.
@@ -7603,6 +8889,8 @@
This variable is only a reference to the real table;
assignments to this variable do not change the
table used by require.
+The real table is stored in the C registry (see §4.3),
+indexed by the key LUA_PRELOAD_TABLE, a string.
@@ -7612,7 +8900,7 @@
When looking for a module,
require calls each of these searchers in ascending order,
with the module name (the argument given to require) as its
-sole parameter.
-The function can return another function (the module loader)
-plus an extra value that will be passed to that loader,
-or a string explaining why it did not find that module
+sole argument.
+If the searcher finds the module,
+it returns another function, the module loader,
+plus an extra value, a loader data,
+that will be passed to that loader and
+returned as a second result by require.
+If it cannot find the module,
+it returns a string explaining why
(or nil if it has nothing to say).
@@ -7665,9 +8957,9 @@
concatenated with a copy of the module name where each dot
is replaced by an underscore.
Moreover, if the module name has a hyphen,
-its prefix up to (and including) the first hyphen is removed.
-For instance, if the module name is a.v1-b.c,
-the function name will be luaopen_b_c.
+its suffix after (and including) the first hyphen is removed.
+For instance, if the module name is a.b.c-v2.1,
+the function name will be luaopen_a_b_c.
All searchers except the first one (preload) return as the extra value
-the file name where the module was found,
+the file path where the module was found,
as returned by package.searchpath.
-The first searcher returns no extra value.
+The first searcher always returns the string ":preload:".
+
+
+
+Searchers should raise no errors and have no side effects in Lua.
+(They may have side effects in C,
+for instance by linking the application with a library.)
@@ -7729,7 +9027,7 @@
Returns the resulting name of the first file that it can
open in read mode (after closing the file),
-or nil plus an error message if none succeeds.
+or fail plus an error message if none succeeds.
(This error message lists all file names it tried to open.)
@@ -7740,6 +9038,8 @@
This library provides generic functions for string manipulation,
such as finding and extracting substrings, and pattern matching.
@@ -7766,7 +9066,7 @@
-Returns the internal numerical codes of the characters s[i],
+Returns the internal numeric codes of the characters s[i],
s[i+1], ..., s[j].
The default value for i is 1;
the default value for j is i.
@@ -7775,7 +9075,7 @@
Receives zero or more integers.
Returns a string with length equal to the number of arguments,
-in which each character has the internal numerical code equal
+in which each character has the internal numeric code equal
to its corresponding argument.
-Numerical codes are not necessarily portable across platforms.
+Numeric codes are not necessarily portable across platforms.
-Returns a string containing a binary representation of the given function,
+Returns a string containing a binary representation
+(a binary chunk)
+of the given function,
so that a later load on this string returns
a copy of the function (but with new upvalues).
+If strip is a true value,
+the binary representation may not include all debug information
+about the function,
+to save space.
+
+
+
+Functions with upvalues have only their number of upvalues saved.
+When (re)loaded,
+those upvalues receive fresh instances.
+(See the load function for details about
+how these upvalues are initialized.
+You can use the debug library to serialize
+and reload the upvalues of a function
+in a way adequate to your needs.)
@@ -7812,18 +9129,17 @@
Looks for the first match of
-pattern in the string s.
+pattern (see §6.4.1) in the string s.
If it finds a match, then find returns the indices of s
where this occurrence starts and ends;
-otherwise, it returns nil.
-A third, optional numerical argument init specifies
+otherwise, it returns fail.
+A third, optional numeric argument init specifies
where to start the search;
its default value is 1 and can be negative.
-A value of true as a fourth, optional argument plain
+A true as a fourth, optional argument plain
turns off the pattern matching facilities,
so the function does a plain "find substring" operation,
with no characters in pattern being considered magic.
-Note that if plain is given, then init must be given as well.
Returns a formatted version of its variable number of arguments
-following the description given in its first argument (which must be a string).
-The format string follows the same rules as the C function sprintf.
-The only differences are that the options/modifiers
-*, h, L, l, n,
-and p are not supported
-and that there is an extra option, q.
-The q option formats a string between double quotes,
+following the description given in its first argument,
+which must be a string.
+The format string follows the same rules as the ISO C function sprintf.
+The only differences are that the conversion specifiers and modifiers
+F, n, *, h, L, and l are not supported
+and that there is an extra specifier, q.
+Both width and precision, when present,
+are limited to two digits.
+
+
+
+The specifier q formats booleans, nil, numbers, and strings
+in a way that the result is a valid constant in Lua source code.
+Booleans and nil are written in the obvious way
+(true, false, nil).
+Floats are written in hexadecimal,
+to preserve full precision.
+A string is written between double quotes,
using escape sequences when necessary to ensure that
it can safely be read back by the Lua interpreter.
For instance, the call
@@ -7860,35 +9187,53 @@
+This specifier does not support modifiers (flags, width, precision).
+
-Options
-A and a (when available),
-E, e, f,
+The conversion specifiers
+A, a, E, e, f,
G, and g all expect a number as argument.
-Options c, d,
+The specifiers c, d,
i, o, u, X, and x
-also expect a number,
-but the range of that number may be limited by
-the underlying C implementation.
-For options o, u, X, and x,
-the number cannot be negative.
-Option q expects a string;
-option s expects a string without embedded zeros.
-If the argument to option s is not a string,
+expect an integer.
+When Lua is compiled with a C89 compiler,
+the specifiers A and a (hexadecimal floats)
+do not support modifiers.
+
+
+
+The specifier s expects a string;
+if its argument is not a string,
it is converted to one following the same rules of tostring.
+If the specifier has any modifier,
+the corresponding string argument should not contain embedded zeros.
+
+
+
+The specifier p formats the pointer
+returned by lua_topointer.
+That gives a unique string identifier for tables, userdata,
+threads, strings, and functions.
+For other values (numbers, nil, booleans),
+this specifier results in a string representing
+the pointer NULL.
Returns an iterator function that,
each time it is called,
-returns the next captures from pattern over the string s.
+returns the next captures from pattern (see §6.4.1)
+over the string s.
If pattern specifies no captures,
then the whole match is produced in each call.
+A third, optional numeric argument init specifies
+where to start the search;
+its default value is 1 and can be negative.
Returns a copy of s
in which all (or the first n, if given)
-occurrences of the pattern have been
+occurrences of the pattern (see §6.4.1) have been
replaced by a replacement string specified by repl,
which can be a string, a table, or a function.
gsub also returns, as its second value,
@@ -7937,9 +9282,9 @@
The character % works as an escape character:
any sequence in repl of the form %d,
with d between 1 and 9,
-stands for the value of the d-th captured substring.
-The sequence %0 stands for the whole match.
-The sequence %% stands for a single %.
+stands for the value of the d-th captured substring;
+the sequence %0 stands for the whole match;
+the sequence %% stands for a single %.
Receives a string and returns a copy of this string with all
uppercase letters changed to lowercase.
All other characters are left unchanged.
@@ -8018,32 +9369,72 @@
Looks for the first match of
-pattern in the string s.
+the pattern (see §6.4.1) in the string s.
If it finds one, then match returns
the captures from the pattern;
-otherwise it returns nil.
+otherwise it returns fail.
If pattern specifies no captures,
then the whole match is returned.
-A third, optional numerical argument init specifies
+A third, optional numeric argument init specifies
where to start the search;
its default value is 1 and can be negative.
+
+Returns a binary string containing the values v1, v2, etc.
+serialized in binary form (packed)
+according to the format string fmt (see §6.4.2).
+
+
+
+
+
+Returns the length of a string resulting from string.pack
+with the given format.
+The format string cannot have the variable-length options
+'s' or 'z' (see §6.4.2).
+
+
+
+
Returns a string that is the concatenation of n copies of
the string s separated by the string sep.
The default value for sep is the empty string
(that is, no separator).
+Returns the empty string if n is not positive.
+
+
+
+(Note that it is very easy to exhaust the memory of your machine
+with a single call to this function.)
In particular,
the call string.sub(s,1,j) returns a prefix of s
with length j,
-and string.sub(s, -i) returns a suffix of s
+and string.sub(s, -i) (for a positive i)
+returns a suffix of s
with length i.
@@ -8076,8 +9471,26 @@
+Returns the values packed in string s (see string.pack)
+according to the format string fmt (see §6.4.2).
+An optional pos marks where
+to start reading in s (default is 1).
+After the read values,
+this function also returns the index of the first unread byte in s.
+
+
+
+
Receives a string and returns a copy of this string with all
lowercase letters changed to uppercase.
All other characters are left unchanged.
@@ -8085,9 +9498,28 @@
+Patterns in Lua are described by regular strings,
+which are interpreted as patterns by the pattern-matching functions
+string.find,
+string.gmatch,
+string.gsub,
+and string.match.
+This section describes the syntax and the meaning
+(that is, what they match) of these strings.
+
+
+
+
+
Character Class:
A character class is used to represent a set of characters.
The following combinations are allowed in describing a character class:
@@ -8125,9 +9557,9 @@
Character Class:
%x: (where x is any non-alphanumeric character)
represents the character x.
This is the standard way to escape the magic characters.
-Any punctuation character (even the non magic)
-can be preceded by a '%'
-when used to represent itself in a pattern.
+Any non-alphanumeric character
+(including all punctuation characters, even the non-magical)
+can be preceded by a '%' to represent itself in a pattern.
[set]:
@@ -8135,7 +9567,7 @@
Character Class:
characters in set.
A range of characters can be specified by
separating the end characters of the range,
-in ascending order, with a '-',
+in ascending order, with a '-'.
All classes %x described above can also be used as
components in set.
All other characters in set represent themselves.
@@ -8146,6 +9578,14 @@
Character Class:
the lowercase letters plus the '-' character.
+
+You can put a closing square bracket in a set
+by positioning it as the first character in the set.
+You can put a hyphen in a set
+by positioning it as the first or the last character in the set.
+(You can also use an escape for both cases.)
+
+
The interaction between ranges and classes is not defined.
Therefore, patterns like [%a-z] or [a-%%]
@@ -8184,26 +9624,27 @@
Pattern Item:
a single character class followed by '*',
-which matches 0 or more repetitions of characters in the class.
+which matches sequences of zero or more characters in the class.
These repetition items will always match the longest possible sequence;
a single character class followed by '+',
-which matches 1 or more repetitions of characters in the class.
+which matches sequences of one or more characters in the class.
These repetition items will always match the longest possible sequence;
a single character class followed by '-',
-which also matches 0 or more repetitions of characters in the class.
+which also matches sequences of zero or more characters in the class.
Unlike '*',
these repetition items will always match the shortest possible sequence;
a single character class followed by '?',
-which matches 0 or 1 occurrence of a character in the class;
+which matches zero or one occurrence of a character in the class.
+It always matches one occurrence if possible;
@@ -8259,13 +9700,13 @@
Captures:
Captures are numbered according to their left parentheses.
For instance, in the pattern "(a*(.)%w(%s*))",
the part of the string matching "a*(.)%w(%s*)" is
-stored as the first capture (and therefore has number 1);
+stored as the first capture, and therefore has number 1;
the character matching "." is captured with number 2,
and the part matching "%s*" has number 3.
-As a special case, the empty capture () captures
+As a special case, the capture () captures
the current string position (a number).
For instance, if we apply the pattern "()aa()" on the
string "flaaap", there will be two captures: 3 and 5.
@@ -8274,683 +9715,772 @@
Captures:
+
Multiple matches:
+The function string.gsub and the iterator string.gmatch
+match multiple occurrences of the given pattern in the subject.
+For these functions,
+a new match is considered valid only
+if it ends at least one byte after the end of the previous match.
+In other words, the pattern machine never accepts the
+empty string as a match immediately after another match.
+As an example,
+consider the results of the following code:
+
+The second and third results come from Lua matching an empty
+string after 'b' and another one after 'c'.
+Lua does not match an empty string after 'a',
+because it would end at the same position of the previous match.
-
-Remember that, whenever an operation needs the length of a table,
-the table should be a proper sequence
-or have a __len metamethod (see §3.4.6).
-All functions ignore non-numeric keys
-in tables given as arguments.
+The first argument to string.pack,
+string.packsize, and string.unpack
+is a format string,
+which describes the layout of the structure being created or read.
-For performance reasons,
-all table accesses (get/set) performed by these functions are raw.
-
+A format string is a sequence of conversion options.
+The conversion options are as follows:
-
![n]: sets maximum alignment to n
+(default is native alignment)
+
b: a signed byte (char)
+
B: an unsigned byte (char)
+
h: a signed short (native size)
+
H: an unsigned short (native size)
+
l: a signed long (native size)
+
L: an unsigned long (native size)
+
j: a lua_Integer
+
J: a lua_Unsigned
+
T: a size_t (native size)
+
i[n]: a signed int with n bytes
+(default is native size)
+
I[n]: an unsigned int with n bytes
+(default is native size)
+
f: a float (native size)
+
d: a double (native size)
+
n: a lua_Number
+
cn: a fixed-sized string with n bytes
+
z: a zero-terminated string
+
s[n]: a string preceded by its length
+coded as an unsigned integer with n bytes
+(default is a size_t)
+
x: one byte of padding
+
Xop: an empty item that aligns
+according to option op
+(which is otherwise ignored)
+
'': (space) ignored
+
+(A "[n]" means an optional integral numeral.)
+Except for padding, spaces, and configurations
+(options "xX <=>!"),
+each option corresponds to an argument in string.pack
+or a result in string.unpack.
-Given a list where all elements are strings or numbers,
-returns list[i]..sep..list[i+1] ··· sep..list[j].
-The default value for sep is the empty string,
-the default for i is 1,
-and the default for j is #list.
-If i is greater than j, returns the empty string.
+For options "!n", "sn", "in", and "In",
+n can be any integer between 1 and 16.
+All integral options check overflows;
+string.pack checks whether the given value fits in the given size;
+string.unpack checks whether the read value fits in a Lua integer.
+For the unsigned options,
+Lua integers are treated as unsigned values too.
+
+Any format string starts as if prefixed by "!1=",
+that is,
+with maximum alignment of 1 (no alignment)
+and native endianness.
+Native endianness assumes that the whole system is
+either big or little endian.
+The packing functions will not emulate correctly the behavior
+of mixed-endian formats.
-Inserts element value at position pos in list,
-shifting up the elements
-list[pos], list[pos+1], ···, list[#list].
-The default value for pos is #list+1,
-so that a call table.insert(t,x) inserts x at the end
-of list t.
+Alignment works as follows:
+For each option,
+the format gets extra padding until the data starts
+at an offset that is a multiple of the minimum between the
+option size and the maximum alignment;
+this minimum must be a power of 2.
+Options "c" and "z" are not aligned;
+option "s" follows the alignment of its starting integer.
+
-Returns a new table with all parameters stored into keys 1, 2, etc.
-and with a field "n" with the total number of parameters.
-Note that the resulting table may not be a sequence.
+
+This library provides basic support for UTF-8 encoding.
+It provides all its functions inside the table utf8.
+This library does not provide any support for Unicode other
+than the handling of the encoding.
+Any operation that needs the meaning of a character,
+such as character classification, is outside its scope.
-Removes from list the element at position pos,
-shifting down the elements
-list[pos+1], list[pos+2], ···, list[#list]
-and erasing element list[#list].
-Returns the value of the removed element.
-The default value for pos is #list,
-so that a call table.remove(t) removes the last element
-of list t.
+Unless stated otherwise,
+all functions that expect a byte position as a parameter
+assume that the given position is either the start of a byte sequence
+or one plus the length of the subject string.
+As in the string library,
+negative indices count from the end of the string.
+
+Functions that create byte sequences
+accept all values up to 0x7FFFFFFF,
+as defined in the original UTF-8 specification;
+that implies byte sequences of up to six bytes.
+Functions that interpret byte sequences only accept
+valid sequences (well formed and not overlong).
+By default, they only accept byte sequences
+that result in valid Unicode code points,
+rejecting values greater than 10FFFF and surrogates.
+A boolean argument lax, when available,
+lifts these checks,
+so that all values up to 0x7FFFFFFF are accepted.
+(Not well formed and overlong sequences are still rejected.)
-Sorts list elements in a given order, in-place,
-from list[1] to list[#list].
-If comp is given,
-then it must be a function that receives two list elements
-and returns true when the first element must come
-before the second in the final order
-(so that not comp(list[i+1],list[i]) will be true after the sort).
-If comp is not given,
-then the standard Lua operator < is used instead.
+
-The sort algorithm is not stable;
-that is, elements considered equal by the given order
-may have their relative positions changed by the sort.
+Receives zero or more integers,
+converts each one to its corresponding UTF-8 byte sequence
+and returns a string with the concatenation of all these sequences.
-Returns the elements from the given table.
-This function is equivalent to
-
-
- return list[i], list[i+1], ···, list[j]
-
-By default, i is 1 and j is #list.
-
+The pattern (a string, not a function) "[\0-\x7F\xC2-\xFD][\x80-\xBF]*"
+(see §6.4.1),
+which matches exactly one UTF-8 byte sequence,
+assuming that the subject is a valid UTF-8 string.
-
-
-
+will iterate over all UTF-8 characters in string s,
+with p being the position (in bytes) and c the code point
+of each character.
+It raises an error if it meets any invalid byte sequence.
-Returns the arc cosine of x (in radians).
+Returns the code points (as integers) from all characters in s
+that start between byte position i and j (both included).
+The default for i is 1 and for j is i.
+It raises an error if it meets any invalid byte sequence.
-Returns the arc sine of x (in radians).
+Returns the number of UTF-8 characters in string s
+that start between positions i and j (both inclusive).
+The default for i is 1 and for j is -1.
+If it finds any invalid byte sequence,
+returns fail plus the position of the first invalid byte.
-Returns the arc tangent of x (in radians).
-
-
+Returns the position (in bytes) where the encoding of the
+n-th character of s
+(counting from position i) starts.
+A negative n gets characters before position i.
+The default for i is 1 when n is non-negative
+and #s + 1 otherwise,
+so that utf8.offset(s, -n) gets the offset of the
+n-th character from the end of the string.
+If the specified character is neither in the subject
+nor right after its end,
+the function returns fail.
+As a special case,
+when n is 0 the function returns the start of the encoding
+of the character that contains the i-th byte of s.
-Returns the arc tangent of y/x (in radians),
-but uses the signs of both parameters to find the
-quadrant of the result.
-(It also handles correctly the case of x being zero.)
+This function assumes that s is a valid UTF-8 string.
-
+This library provides generic functions for table manipulation.
+It provides all its functions inside the table table.
-Returns the cosine of x (assumed to be in radians).
-
-
+Remember that, whenever an operation needs the length of a table,
+all caveats about the length operator apply (see §3.4.7).
+All functions ignore non-numeric keys
+in the tables given as arguments.
-Returns the hyperbolic cosine of x.
+Given a list where all elements are strings or numbers,
+returns the string list[i]..sep..list[i+1] ··· sep..list[j].
+The default value for sep is the empty string,
+the default for i is 1,
+and the default for j is #list.
+If i is greater than j, returns the empty string.
-Returns the angle x (given in radians) in degrees.
+Inserts element value at position pos in list,
+shifting up the elements
+list[pos], list[pos+1], ···, list[#list].
+The default value for pos is #list+1,
+so that a call table.insert(t,x) inserts x at the end
+of the list t.
+
+
+
+Moves elements from the table a1 to the table a2,
+performing the equivalent to the following
+multiple assignment:
+a2[t],··· = a1[f],···,a1[e].
+The default for a2 is a1.
+The destination range can overlap with the source range.
+The number of elements to be moved must fit in a Lua integer.
-Returns the value ex.
+Returns the destination table a2.
-Returns the largest integer smaller than or equal to x.
+Returns a new table with all arguments stored into keys 1, 2, etc.
+and with a field "n" with the total number of arguments.
+Note that the resulting table may not be a sequence,
+if some arguments are nil.
-Returns the remainder of the division of x by y
-that rounds the quotient towards zero.
+Removes from list the element at position pos,
+returning the value of the removed element.
+When pos is an integer between 1 and #list,
+it shifts down the elements
+list[pos+1], list[pos+2], ···, list[#list]
+and erases element list[#list];
+The index pos can also be 0 when #list is 0,
+or #list + 1.
+
+The default value for pos is #list,
+so that a call table.remove(l) removes the last element
+of the list l.
-
+Sorts the list elements in a given order, in-place,
+from list[1] to list[#list].
+If comp is given,
+then it must be a function that receives two list elements
+and returns true when the first element must come
+before the second in the final order,
+so that, after the sort,
+i <= j implies not comp(list[j],list[i]).
+If comp is not given,
+then the standard Lua operator < is used instead.
+The comp function must define a consistent order;
+more formally, the function must define a strict weak order.
+(A weak order is similar to a total order,
+but it can equate different elements for comparison purposes.)
-The value HUGE_VAL,
-a value larger than or equal to any other numerical value.
+The sort algorithm is not stable:
+Different elements considered equal by the given order
+may have their relative positions changed by the sort.
+This library provides basic mathematical functions.
+It provides all its functions and constants inside the table math.
+Functions with the annotation "integer/float" give
+integer results for integer arguments
+and float results for non-integer arguments.
+The rounding functions
+math.ceil, math.floor, and math.modf
+return an integer when the result fits in the range of an integer,
+or a float otherwise.
-The value of π.
+
+Returns the arc tangent of y/x (in radians),
+using the signs of both arguments to find the
+quadrant of the result.
+It also handles correctly the case of x being zero.
+
+The default value for x is 1,
+so that the call math.atan(y)
+returns the arc tangent of y.
-
-This function is an interface to the simple
-pseudo-random generator function rand provided by Standard C.
-(No guarantees can be given for its statistical properties.)
+
-When called without arguments,
-returns a uniform pseudo-random real number
-in the range [0,1).
-When called with an integer number m,
-math.random returns
-a uniform pseudo-random integer in the range [1, m].
-When called with two integer numbers m and n,
-math.random returns a uniform pseudo-random
-integer in the range [m, n].
+Converts the angle x from radians to degrees.
-Sets x as the "seed"
-for the pseudo-random generator:
-equal seeds produce equal sequences of numbers.
+Returns the value ex
+(where e is the base of natural logarithms).
-Returns the square root of x.
-(You can also use the expression x^0.5 to compute this value.)
+The float value HUGE_VAL,
+a value greater than any other numeric value.
-Returns the tangent of x (assumed to be in radians).
+Returns the logarithm of x in the given base.
+The default for base is e
+(so that the function returns the natural logarithm of x).
-This library provides bitwise operations.
-It provides all its functions inside the table bit32.
-Unless otherwise stated,
-all functions accept numeric arguments in the range
-(-251,+251);
-each argument is normalized to
-the remainder of its division by 232
-and truncated to an integer (in some unspecified way),
-so that its final value falls in the range [0,232 - 1].
-Similarly, all results are in the range [0,232 - 1].
-Note that bit32.bnot(0) is 0xFFFFFFFF,
-which is different from -1.
+
+Returns the argument with the minimum value,
+according to the Lua operator <.
-
-Returns the number x shifted disp bits to the right.
-The number disp may be any representable integer.
-Negative displacements shift to the left.
-This shift operation is what is called arithmetic shift.
-Vacant bits on the left are filled
-with copies of the higher bit of x;
-vacant bits on the right are filled with zeros.
-In particular,
-displacements with absolute values higher than 31
-result in zero or 0xFFFFFFFF (all original bits are shifted out).
+
-Returns a boolean signaling
-whether the bitwise and of its operands is different from zero.
-
-
+When called without arguments,
+returns a pseudo-random float with uniform distribution
+in the range [0,1).
+When called with two integers m and n,
+math.random returns a pseudo-random integer
+with uniform distribution in the range [m, n].
+The call math.random(n), for a positive n,
+is equivalent to math.random(1,n).
+The call math.random(0) produces an integer with
+all bits (pseudo)random.
+This function uses the xoshiro256** algorithm to produce
+pseudo-random 64-bit integers,
+which are the results of calls with argument 0.
+Other results (ranges and floats)
+are unbiased extracted from these integers.
-Returns the bitwise exclusive or of its operands.
+Lua initializes its pseudo-random generator with the equivalent of
+a call to math.randomseed with no arguments,
+so that math.random should generate
+different sequences of results each time the program runs.
-Returns the unsigned number formed by the bits
-field to field + width - 1 from n.
-Bits are numbered from 0 (least significant) to 31 (most significant).
-All accessed bits must be in the range [0, 31].
+When called with at least one argument,
+the integer parameters x and y are
+joined into a 128-bit seed that
+is used to reinitialize the pseudo-random generator;
+equal seeds produce equal sequences of numbers.
+The default for y is zero.
-The default for width is 1.
-
-
+When called with no arguments,
+Lua generates a seed with
+a weak attempt for randomness.
+This function returns the two seed components
+that were effectively used,
+so that setting them again repeats the sequence.
-Returns a copy of n with
-the bits field to field + width - 1
-replaced by the value v.
-See bit32.extract for details about field and width.
+To ensure a required level of randomness to the initial state
+(or contrarily, to have a deterministic sequence,
+for instance when debugging a program),
+you should call math.randomseed with explicit arguments.
-Returns the number x rotated disp bits to the left.
-The number disp may be any representable integer.
-
+Returns the sine of x (assumed to be in radians).
-
-For any valid displacement,
-the following identity holds:
-
+Returns the square root of x.
+(You can also use the expression x^0.5 to compute this value.)
-
-Returns the number x shifted disp bits to the left.
-The number disp may be any representable integer.
-Negative displacements shift to the right.
-In any direction, vacant bits are filled with zeros.
-In particular,
-displacements with absolute values higher than 31
-result in zero (all bits are shifted out).
-For positive displacements,
-the following equality holds:
+
-In particular,
-negative displacements rotate to the left.
+If the value x is convertible to an integer,
+returns that integer.
+Otherwise, returns fail.
-Returns the number x shifted disp bits to the right.
-The number disp may be any representable integer.
-Negative displacements shift to the left.
-In any direction, vacant bits are filled with zeros.
-In particular,
-displacements with absolute values higher than 31
-result in zero (all bits are shifted out).
+Returns "integer" if x is an integer,
+"float" if it is a float,
+or fail if x is not a number.
+
+
-For positive displacements,
-the following equality holds:
+
-This shift operation is what is called logical shift.
+Returns a boolean,
+true if and only if integer m is below integer n when
+they are compared as unsigned integers.
@@ -8962,34 +10492,45 @@
The I/O library provides two different styles for file manipulation.
-The first one uses implicit file descriptors;
+The first one uses implicit file handles;
that is, there are operations to set a default input file and a
default output file,
-and all input/output operations are over these default files.
-The second style uses explicit file descriptors.
+and all input/output operations are done over these default files.
+The second style uses explicit file handles.
-When using implicit file descriptors,
+When using implicit file handles,
all operations are supplied by table io.
-When using explicit file descriptors,
-the operation io.open returns a file descriptor
-and then all operations are supplied as methods of the file descriptor.
+When using explicit file handles,
+the operation io.open returns a file handle
+and then all operations are supplied as methods of the file handle.
+
+
+
+The metatable for file handles provides metamethods
+for __gc and __close that try
+to close the file when called.
The table io also provides
-three predefined file descriptors with their usual meanings from C:
+three predefined file handles with their usual meanings from C:
io.stdin, io.stdout, and io.stderr.
The I/O library never closes these files.
Unless otherwise stated,
-all I/O functions return nil on failure
-(plus an error message as a second result and
-a system-dependent error code as a third result)
-and some value different from nil on success.
+all I/O functions return fail on failure,
+plus an error message as a second result and
+a system-dependent error code as a third result,
+and some non-false value on success.
+On non-POSIX systems,
+the computation of the error message and error code
+in case of errors
+may be not thread safe,
+because they rely on the global C variable errno.
and sets its handle as the default input file.
When called with a file handle,
it simply sets this file handle as the default input file.
-When called without parameters,
+When called without arguments,
it returns the current default input file.
@@ -9034,26 +10575,34 @@
Opens the given file name in read mode
and returns an iterator function that
works like file:lines(···) over the opened file.
-When the iterator function detects the end of file,
-it returns nil (to finish the loop) and automatically closes the file.
+When the iterator function fails to read any value,
+it automatically closes the file.
+Besides the iterator function,
+io.lines returns three other values:
+two nil values as placeholders,
+plus the created file handle.
+Therefore, when used in a generic for loop,
+the file is closed also if the loop is interrupted by an
+error or a break.
The call io.lines() (with no file name) is equivalent
-to io.input():lines();
+to io.input():lines("l");
that is, it iterates over the lines of the default input file.
-In this case it does not close the file when the loop ends.
+In this case, the iterator does not close the file when the loop ends.
-In case of errors this function raises the error,
+In case of errors opening the file,
+this function raises the error,
instead of returning an error code.
@@ -9066,8 +10615,8 @@
This function opens a file,
in the mode specified in the string mode.
-It returns a new file handle,
-or, in case of errors, nil plus an error message.
+In case of success,
+it returns a new file handle.
-Starts program prog in a separated process and returns
+Starts the program prog in a separated process and returns
a file handle that you can use to read data from this program
(if mode is "r", the default)
or to write data to this program
@@ -9132,7 +10681,8 @@
-Returns a handle for a temporary file.
+In case of success,
+returns a handle for a temporary file.
This file is opened in update mode
and it is automatically removed when the program ends.
@@ -9147,7 +10697,7 @@
Checks whether obj is a valid file handle.
Returns the string "file" if obj is an open file handle,
"closed file" if obj is a closed file handle,
-or nil if obj is not a file handle.
+or fail if obj is not a file handle.
@@ -9200,7 +10750,7 @@
each time it is called,
reads the file according to the given formats.
When no format is given,
-uses "*l" as a default.
+uses "l" as a default.
As an example, the construction
Reads the file file,
according to the given formats, which specify what to read.
For each format,
-the function returns a string (or a number) with the characters read,
-or nil if it cannot read data with the specified format.
-When called without formats,
+the function returns a string or a number with the characters read,
+or fail if it cannot read data with the specified format.
+(In this latter case,
+the function does not read subsequent formats.)
+When called without arguments,
it uses a default format that reads the next line
(see below).
@@ -9239,36 +10786,46 @@
"*n":
-reads a number;
-this is the only format that returns a number instead of a string.
+
"n":
+reads a numeral and returns it as a float or an integer,
+following the lexical conventions of Lua.
+(The numeral may have leading whitespaces and a sign.)
+This format always reads the longest input sequence that
+is a valid prefix for a numeral;
+if that prefix does not form a valid numeral
+(e.g., an empty string, "0x", or "3.4e-")
+or it is too long (more than 200 characters),
+it is discarded and the format returns fail.
-
"*a":
+
"a":
reads the whole file, starting at the current position.
-On end of file, it returns the empty string.
+On end of file, it returns the empty string;
+this format never fails.
-
"*l":
+
"l":
reads the next line skipping the end of line,
-returning nil on end of file.
+returning fail on end of file.
This is the default format.
-
"*L":
-reads the next line keeping the end of line (if present),
-returning nil on end of file.
+
"L":
+reads the next line keeping the end-of-line character (if present),
+returning fail on end of file.
number:
reads a string with up to this number of bytes,
-returning nil on end of file.
-If number is zero,
+returning fail on end of file.
+If number is zero,
it reads nothing and returns an empty string,
-or nil on end of file.
+or fail on end of file.
-
+
+The formats "l" and "L" should be used only for text files.
+
@@ -9289,7 +10846,7 @@
In case of success, seek returns the final file position,
measured in bytes from the beginning of the file.
-If seek fails, it returns nil,
+If seek fails, it returns fail,
plus a string describing the error.
@@ -9311,31 +10868,25 @@
-Sets the buffering mode for an output file.
+Sets the buffering mode for a file.
There are three available modes:
+
"no": no buffering.
+
"full": full buffering.
+
"line": line buffering.
+
-
"no":
-no buffering; the result of any output operation appears immediately.
-
-
-
"full":
-full buffering; output operation is performed only
-when the buffer is full or when
-you explicitly flush the file (see io.flush).
-
+
+For the last two cases,
+size is a hint for the size of the buffer, in bytes.
+The default is an appropriate size.
-
"line":
-line buffering; output is buffered until a newline is output
-or there is any input from some special files
-(such as a terminal device).
-
-
-For the last two cases, size
-specifies the size of the buffer, in bytes.
-The default is an appropriate size.
+
+The specific behavior of each mode is non portable;
+check the underlying ISO C function setvbuf in your platform for
+more details.
@@ -9351,7 +10902,6 @@
Returns an approximation of the amount in seconds of CPU time
-used by the program.
+used by the program,
+as returned by the underlying ISO C function clock.
@@ -9398,10 +10949,11 @@
After this optional character,
if format is the string "*t",
then date returns a table with the following fields:
-year (four digits), month (1–12), day (1–31),
-hour (0–23), min (0–59), sec (0–61),
-wday (weekday, Sunday is 1),
-yday (day of the year),
+year, month (1–12), day (1–31),
+hour (0–23), min (0–59),
+sec (0–61, due to leap seconds),
+wday (weekday, 1–7, Sunday is 1),
+yday (day of the year, 1–366),
and isdst (daylight saving flag, a boolean).
This last field may be absent
if the information is not available.
@@ -9410,19 +10962,19 @@
If format is not "*t",
then date returns the date as a string,
-formatted according to the same rules as the C function strftime.
+formatted according to the same rules as the ISO C function strftime.
-When called without arguments,
-date returns a reasonable date and time representation that depends on
-the host system and on the current locale
-(that is, os.date() is equivalent to os.date("%c")).
+If format is absent, it defaults to "%c",
+which gives a human-readable date and time representation
+using the current locale.
-On some systems,
-this function may be not thread safe.
+On non-POSIX systems,
+this function may be not thread safe
+because of its reliance on C function gmtime and C function localtime.
@@ -9432,7 +10984,9 @@
-Returns the number of seconds from time t1 to time t2.
+Returns the difference, in seconds,
+from time t1 to time t2
+(where the times are values returned by os.time).
In POSIX, Windows, and some other systems,
this value is exactly t2-t1.
@@ -9444,13 +10998,13 @@
-This function is equivalent to the C function system.
+This function is equivalent to the ISO C function system.
It passes command to be executed by an operating system shell.
Its first result is true
if the command terminated successfully,
-or nil otherwise.
+or fail otherwise.
After this first result
-the function returns a string and a number,
+the function returns a string plus a number,
as follows:
-Calls the C function exit to terminate the host program.
+Calls the ISO C function exit to terminate the host program.
If code is true,
the returned status is EXIT_SUCCESS;
if code is false,
@@ -9491,7 +11045,7 @@
If the optional second argument close is true,
-closes the Lua state before exiting.
+the function closes the Lua state before exiting (see lua_close).
@@ -9501,8 +11055,8 @@
-Returns the value of the process environment variable varname,
-or nil if the variable is not defined.
+Returns the value of the process environment variable varname
+or fail if the variable is not defined.
@@ -9514,8 +11068,9 @@
Deletes the file (or empty directory, on POSIX systems)
with the given name.
-If this function fails, it returns nil,
+If this function fails, it returns fail
plus a string describing the error and the error code.
+Otherwise, it returns true.
@@ -9525,9 +11080,10 @@
-Renames file or directory named oldname to newname.
-If this function fails, it returns nil,
+Renames the file or directory named oldname to newname.
+If this function fails, it returns fail,
plus a string describing the error and the error code.
+Otherwise, it returns true.
@@ -9544,7 +11100,7 @@
"monetary", "numeric", or "time";
the default category is "all".
The function returns the name of the new locale,
-or nil if the request cannot be honored.
+or fail if the request cannot be honored.
Returns the current time when called without arguments,
-or a time representing the date and time specified by the given table.
+or a time representing the local date and time specified by the given table.
This table must have fields year, month, and day,
and may have fields
hour (default is 12),
min (default is 0),
sec (default is 0),
and isdst (default is nil).
+Other fields are ignored.
For a description of these fields, see the os.date function.
+
+When the function is called,
+the values in these fields do not need to be inside their valid ranges.
+For instance, if sec is -10,
+it means 10 seconds before the time specified by the other fields;
+if hour is 1000,
+it means 1000 hours after the time specified by the other fields.
+
+
The returned value is a number, whose meaning depends on your system.
In POSIX, Windows, and some other systems,
@@ -9588,6 +11159,14 @@
+When called with a table,
+os.time also normalizes all the fields
+documented in the os.date function,
+so that they represent the same time as before the call
+but with values inside their valid ranges.
+
+
-On POSIX systems,
+In POSIX systems,
this function also creates a file with that name,
to avoid security risks.
(Someone else might create the file with wrong permissions
@@ -9626,7 +11205,7 @@
This library provides
-the functionality of the debug interface (§4.9) to Lua programs.
+the functionality of the debug interface (§4.7) to Lua programs.
You should exert care when using this library.
Several of its functions
violate basic assumptions about Lua code
@@ -9675,8 +11254,12 @@
Returns the current hook settings of the thread, as three values:
the current hook function, the current hook mask,
-and the current hook count
-(as set by the debug.sethook function).
+and the current hook count,
+as set by the debug.sethook function.
+
+
+
+Returns fail if there is no active hook.
@@ -9693,10 +11276,10 @@
of the given thread:
level 0 is the current function (getinfo itself);
level 1 is the function that called getinfo
-(except for tail calls, which do not count on the stack);
+(except for tail calls, which do not count in the stack);
and so on.
-If f is a number larger than the number of active functions,
-then getinfo returns nil.
+If f is a number greater than the number of active functions,
+then getinfo returns fail.
with the string what describing which fields to fill in.
The default for what is to get all information available,
except the table of valid lines.
-If present,
-the option 'f'
+The option 'f'
adds a field named func with the function itself.
-If present,
-the option 'L'
-adds a field named activelines with the table of
-valid lines.
+The option 'L' adds a field named activelines
+with the table of valid lines,
+provided the function is a Lua function.
+If the function has no debug information,
+the table is empty.
For instance, the expression debug.getinfo(1,"n").name returns
-a table with a name for the current function,
+a name for the current function,
if a reasonable name can be found,
and the expression debug.getinfo(print)
returns a table with all available information
@@ -9732,23 +11315,29 @@
This function returns the name and the value of the local variable
with index local of the function at level f of the stack.
This function accesses not only explicit local variables,
-but also parameters, temporaries, etc.
+but also parameters and temporary values.
The first parameter or local variable has index 1, and so on,
-until the last active variable.
-Negative indices refer to vararg parameters;
--1 is the first vararg parameter.
-The function returns nil if there is no variable with the given index,
+following the order that they are declared in the code,
+counting only the variables that are active
+in the current scope of the function.
+Compile-time constants may not appear in this listing,
+if they were optimized away by the compiler.
+Negative indices refer to vararg arguments;
+-1 is the first vararg argument.
+The function returns fail
+if there is no variable with the given index,
and raises an error when called with a level out of range.
(You can call debug.getinfo to check whether the level is valid.)
-Variable names starting with '(' (open parentheses)
-represent internal variables
-(loop control variables, temporaries, varargs, and C function locals).
+Variable names starting with '(' (open parenthesis)
+represent variables with no known names
+(internal variables such as loop control variables,
+and variables from chunks saved without debug information).
This function returns the name and the value of the upvalue
with index up of the function f.
-The function returns nil if there is no upvalue with the given index.
+The function returns fail
+if there is no upvalue with the given index.
+
+
+
+(For Lua functions,
+upvalues are the external local variables that the function uses,
+and that are consequently included in its closure.)
+
+
+
+For C functions, this function uses the empty string ""
+as a name for all upvalues.
+
+
+
+Variable name '?' (interrogation mark)
+represents variables with no known names
+(variables from chunks saved without debug information).
-Returns the Lua value associated to u.
-If u is not a userdata,
-returns nil.
+Returns the n-th user value associated
+to the userdata u plus a boolean,
+false if the userdata does not have that value.
@@ -9808,10 +11415,10 @@
-Sets the given function as a hook.
+Sets the given function as the debug hook.
The string mask and the number count describe
when the hook will be called.
-The string mask may have the following characters,
+The string mask may have any combination of the following characters,
with the given meaning:
'r': the hook is called every time Lua returns from a function;
'l': the hook is called every time Lua enters a new line of code.
-With a count different from zero,
-the hook is called after every count instructions.
+Moreover,
+with a count different from zero,
+the hook is called also after every count instructions.
When the hook is called, its first parameter is a string
describing the event that has triggered its call:
-"call" (or "tail call"),
-"return",
+"call", "tail call", "return",
"line", and "count".
For line events,
the hook also gets the new line number as its second parameter.
Inside a hook,
you can call getinfo with level 2 to get more information about
-the running function
-(level 0 is the getinfo function,
-and level 1 is the hook function).
+the running function.
+(Level 0 is the getinfo function,
+and level 1 is the hook function.)
@@ -9852,7 +11459,7 @@
This function assigns the value value to the local variable
with index local of the function at level level of the stack.
-The function returns nil if there is no local
+The function returns fail if there is no local
variable with the given index,
and raises an error when called with a level out of range.
(You can call getinfo to check whether the level is valid.)
@@ -9885,26 +11492,30 @@
This function assigns the value value to the upvalue
with index up of the function f.
-The function returns nil if there is no upvalue
+The function returns fail if there is no upvalue
with the given index.
Otherwise, it returns the name of the upvalue.
+
Sets the given value as
-the Lua value associated to the given udata.
-value must be a table or nil;
+the n-th user value associated to the given udata.
udata must be a full userdata.
-Returns udata.
+Returns udata,
+or fail if the userdata does not have that value.
@@ -9918,7 +11529,7 @@
this function returns message without further processing.
Otherwise,
it returns a string with a traceback of the call stack.
-An optional message string is appended
+The optional message string is appended
at the beginning of the traceback.
An optional level number tells at which level
to start the traceback
@@ -9932,7 +11543,7 @@
-Returns an unique identifier (as a light userdata)
+Returns a unique identifier (as a light userdata)
for the upvalue numbered n
from the given function.
@@ -9971,7 +11582,7 @@
called simply lua,
is provided with the standard distribution.
The standalone interpreter includes
-all standard libraries, including the debug library.
+all standard libraries.
Its usage is:
-: executes stdin as a file and stops handling options.
+
-e stat: execute string stat;
+
-i: enter interactive mode after running script;
+
-l mod: "require" mod and assign the
+ result to global mod;
+
-l g=mod: "require" mod and assign the
+ result to global g;
+
-v: print version information;
+
-E: ignore environment variables;
+
-W: turn warnings on;
+
--: stop handling options;
+
-: execute stdin as a file and stop handling options.
-After handling its options, lua runs the given script,
-passing to it the given args as string arguments.
+(The form -l g=mod was introduced in release 5.4.4.)
+
+
+
+After handling its options, lua runs the given script.
When called without arguments,
lua behaves as lua -v -i
when the standard input (stdin) is a terminal,
@@ -9997,9 +11615,9 @@
-When called without option -E,
-the interpreter checks for an environment variable LUA_INIT_5_2
-(or LUA_INIT if it is not defined)
+When called without the option -E,
+the interpreter checks for an environment variable LUA_INIT_5_4
+(or LUA_INIT if the versioned name is not defined)
before running any argument.
If the variable content has the format @filename,
then lua executes the file.
@@ -10007,72 +11625,98 @@
-When called with option -E,
-besides ignoring LUA_INIT,
-Lua also ignores
-the values of LUA_PATH and LUA_CPATH,
-setting the values of
-package.path and package.cpath
-with the default paths defined in luaconf.h.
+When called with the option -E,
+Lua does not consult any environment variables.
+In particular,
+the values of package.path and package.cpath
+are set with the default paths defined in luaconf.h.
+To signal to the libraries that this option is on,
+the stand-alone interpreter sets the field
+"LUA_NOENV" in the registry to a true value.
+Other libraries may consult this field for the same purpose.
-All options are handled in order, except -i and -E.
+The options -e, -l, and -W are handled in
+the order they appear.
For instance, an invocation like
-will first set a to 1, then print the value of a,
+will first set a to 1, then require the library lib1,
and finally run the file script.lua with no arguments.
(Here $ is the shell prompt. Your prompt may be different.)
-Before starting to run the script,
-lua collects all arguments in the command line
+Before running any code,
+lua collects all command-line arguments
in a global table called arg.
-The script name is stored at index 0,
+The script name goes to index 0,
the first argument after the script name goes to index 1,
and so on.
Any arguments before the script name
-(that is, the interpreter name plus the options)
+(that is, the interpreter name plus its options)
go to negative indices.
For instance, in the call
$ lua -la b.lua t1 t2
-the interpreter first runs the file a.lua,
-then creates a table
+the table is like this:
-and finally runs the file b.lua.
-The script is called with arg[1], arg[2], ...
-as arguments;
-it can also access these arguments with the vararg expression '...'.
+If there is no script in the call,
+the interpreter name goes to index 0,
+followed by the other arguments.
+For instance, the call
+
+
+ $ lua -e "print(arg[1])"
+
+will print "-e".
+If there is a script,
+the script is called with arguments
+arg[1], ···, arg[#arg].
+Like all chunks in Lua,
+the script is compiled as a variadic function.
In interactive mode,
-if you write an incomplete statement,
+Lua repeatedly prompts and waits for a line.
+After reading a line,
+Lua first try to interpret the line as an expression.
+If it succeeds, it prints its value.
+Otherwise, it interprets the line as a statement.
+If you write an incomplete statement,
the interpreter waits for its completion
by issuing a different prompt.
+
+If the global variable _PROMPT contains a string,
+then its value is used as the prompt.
+Similarly, if the global variable _PROMPT2 contains a string,
+its value is used as the secondary prompt
+(issued during incomplete statements).
+
+
In case of unprotected errors in the script,
the interpreter reports the error to the standard error stream.
-If the error object is a string,
-the interpreter adds a stack traceback to it.
-Otherwise, if the error object has a metamethod __tostring,
+If the error object is not a string but
+has a metamethod __tostring,
the interpreter calls this metamethod to produce the final message.
-Finally, if the error object is nil,
-the interpreter does not report the error.
+Otherwise, the interpreter converts the error object to a string
+and adds a stack traceback to it.
+When warnings are on,
+they are simply printed in the standard error output.
To allow the use of Lua as a
script interpreter in Unix systems,
-the standalone interpreter skips
-the first line of a chunk if it starts with #.
+Lua skips the first line of a file chunk if it starts with #.
Therefore, Lua scripts can be made into executable programs
by using chmod +x and the #! form,
as in
@@ -10095,7 +11738,7 @@
-(Of course,
+Of course,
the location of the Lua interpreter may be different in your machine.
If lua is in your PATH,
then
@@ -10103,147 +11746,152 @@
Here we list the incompatibilities that you may find when moving a program
-from Lua 5.1 to Lua 5.2.
+from Lua 5.3 to Lua 5.4.
+
+
+
You can avoid some incompatibilities by compiling Lua with
appropriate options (see file luaconf.h).
However,
-all these compatibility options will be removed in the next version of Lua.
-Similarly,
-all features marked as deprecated in Lua 5.1
-have been removed in Lua 5.2.
-
-
-
-
-The concept of environment changed.
-Only Lua functions have environments.
-To set the environment of a Lua function,
-use the variable _ENV or the function load.
+all these compatibility options will be removed in the future.
+More often than not,
+compatibility issues arise when these compatibility options
+are removed.
+So, whenever you have the chance,
+you should try to test your code with a version of Lua compiled
+with all compatibility options turned off.
+That will ease transitions to newer versions of Lua.
-C functions no longer have environments.
-Use an upvalue with a shared table if you need to keep
-shared state among several C functions.
-(You may use luaL_setfuncs to open a C library
-with all functions sharing a common upvalue.)
+Lua versions can always change the C API in ways that
+do not imply source-code changes in a program,
+such as the numeric values for constants
+or the implementation of functions as macros.
+Therefore,
+you should never assume that binaries are compatible between
+different Lua versions.
+Always recompile clients of the Lua API when
+using a new version.
-To manipulate the "environment" of a userdata
-(which is now called user value),
-use the new functions
-lua_getuservalue and lua_setuservalue.
-
+Similarly, Lua versions can always change the internal representation
+of precompiled chunks;
+precompiled chunks are not compatible between different Lua versions.
-
-Lua identifiers cannot use locale-dependent letters.
-
-
-
-Doing a step or a full collection in the garbage collector
-does not restart the collector if it has been stopped.
-
-
-
-Weak tables with weak keys now perform like ephemeron tables.
-
-
-The event tail return in debug hooks was removed.
-Instead, tail calls generate a special new event,
-tail call, so that the debugger can know that
-there will not be a corresponding return event.
-
-
-
-Equality between function values has changed.
-Now, a function definition may not create a new value;
-it may reuse some previous value if there is no
-observable difference to the new function.
-
+
+The standard paths in the official distribution may
+change between versions.
-
-Function module is deprecated.
-It is easy to set up a module with regular Lua code.
-Modules are not expected to set global variables.
+The coercion of strings to numbers in
+arithmetic and bitwise operations
+has been removed from the core language.
+The string library does a similar job
+for arithmetic (but not for bitwise) operations
+using the string metamethods.
+However, unlike in previous versions,
+the new implementation preserves the implicit type of the numeral
+in the string.
+For instance, the result of "1" + "2" now is an integer,
+not a float.
-Functions setfenv and getfenv were removed,
-because of the changes in environments.
+Literal decimal integer constants that overflow are read as floats,
+instead of wrapping around.
+You can use hexadecimal notation for such constants if you
+want the old behavior
+(reading them as integers with wrap around).
-Function math.log10 is deprecated.
-Use math.log with 10 as its second argument, instead.
+The use of the __lt metamethod to emulate __le
+has been removed.
+When needed, this metamethod must be explicitly defined.
-Function loadstring is deprecated.
-Use load instead; it now accepts string arguments
-and are exactly equivalent to loadstring.
+The semantics of the numerical for loop
+over integers changed in some details.
+In particular, the control variable never wraps around.
-Function table.maxn is deprecated.
-Write it in Lua if you really need it.
+A label for a goto cannot be declared where a label with the same
+name is visible, even if this other label is declared in an enclosing
+block.
-Function os.execute now returns true when command
-terminates successfully and nil plus error information
-otherwise.
+When finalizing an object,
+Lua does not ignore __gc metamethods that are not functions.
+Any value will be called, if present.
+(Non-callable values will generate a warning,
+like any other error when calling a finalizer.)
-Function unpack was moved into the table library
-and therefore must be called as table.unpack.
+The function print does not call tostring
+to format its arguments;
+instead, it has this functionality hardwired.
+You should use __tostring to modify how values are printed.
-Character class %z in patterns is deprecated,
-as now patterns may contain '\0' as a regular character.
+The pseudo-random number generator used by the function math.random
+now starts with a somewhat random seed.
+Moreover, it uses a different algorithm.
-The table package.loaders was renamed package.searchers.
+By default, the decoding functions in the utf8 library
+do not accept surrogates as valid code points.
+An extra parameter in these functions makes them more permissive.
-Lua does not have bytecode verification anymore.
-So, all functions that load code
-(load and loadfile)
-are potentially insecure when loading untrusted binary data.
-(Actually, those functions were already insecure because
-of flaws in the verification algorithm.)
-When in doubt,
-use the mode argument of those functions
-to restrict them to loading textual chunks.
+The options "setpause" and "setstepmul"
+of the function collectgarbage are deprecated.
+You should use the new option "incremental" to set them.
-The standard paths in the official distribution may
-change between versions.
+The function io.lines now returns four values,
+instead of just one.
+That can be a problem when it is used as the sole
+argument to another function that has optional parameters,
+such as in load(io.lines(filename, "L")).
+To fix that issue,
+you can wrap the call into parentheses,
+to adjust its number of results to one.
-Function luaL_register is deprecated.
-Use luaL_setfuncs so that your module does not create globals.
-(Modules are not expected to set global variables anymore.)
-
-
-The osize argument to the allocation function
-may not be zero when creating a new block,
-that is, when ptr is NULL
-(see lua_Alloc).
-Use only the test ptr == NULL to check whether
-the block is new.
-
+
-Finalizers (__gc metamethods) for userdata are called in the
-reverse order that they were marked for finalization,
-not that they were created (see §2.5.1).
-(Most userdata are marked immediately after they are created.)
-Moreover,
-if the metatable does not have a __gc field when set,
-the finalizer will not be called,
-even if it is set later.
-
+Full userdata now has an arbitrary number of associated user values.
+Therefore, the functions lua_newuserdata,
+lua_setuservalue, and lua_getuservalue were
+replaced by lua_newuserdatauv,
+lua_setiuservalue, and lua_getiuservalue,
+which have an extra argument.
-
-luaL_typerror was removed.
-Write your own version if you need it.
-
-
-Function lua_cpcall is deprecated.
-You can simply push the function with lua_pushcfunction
-and call it with lua_pcall.
+
+For compatibility, the old names still work as macros assuming
+one single user value.
+Note, however, that userdata with zero user values
+are more efficient memory-wise.
-Functions lua_equal and lua_lessthan are deprecated.
-Use the new lua_compare with appropriate options instead.
+The function lua_resume has an extra parameter.
+This out parameter returns the number of values on
+the top of the stack that were yielded or returned by the coroutine.
+(In previous versions,
+those values were the entire stack.)
-Function lua_objlen was renamed lua_rawlen.
+The function lua_version returns the version number,
+instead of an address of the version number.
+The Lua core should work correctly with libraries using their
+own static copies of the same core,
+so there is no need to check whether they are using the same
+address space.
-Function lua_load has an extra parameter, mode.
-Pass NULL to simulate the old behavior.
+The constant LUA_ERRGCMM was removed.
+Errors in finalizers are never propagated;
+instead, they generate a warning.
-Function lua_resume has an extra parameter, from.
-Pass NULL or the thread doing the call.
+The options LUA_GCSETPAUSE and LUA_GCSETSTEPMUL
+of the function lua_gc are deprecated.
+You should use the new option LUA_GCINC to set them.
Here is the complete syntax of Lua in extended BNF.
-(It does not describe operator precedences.)
+As usual in extended BNF,
+{A} means 0 or more As,
+and [A] means an optional A.
+(For operator precedences, see §3.4.8;
+for a description of the terminals
+Name, Numeral,
+and LiteralString, see §3.1.)
@@ -10357,7 +11989,11 @@
for namelist in explist do block end |
function funcname funcbody |
localfunction Name funcbody |
- local namelist [‘=’ explist]
+ local attnamelist [‘=’ explist]
+
+ attnamelist ::= Name attrib {‘,’ Name attrib}
+
+ attrib ::= [‘<’ Name ‘>’]
retstat ::= return [explist] [‘;’]
@@ -10373,14 +12009,14 @@
-Lua 5.2 Reference Manual
+