Add format_string routine to format other types to strings

doc/specs/stdlib_ascii.md

@@ -212,42 +212,4 @@ program demo_reverse
     implicit none
     print'(a)', reverse("Hello, World!") ! returns "!dlroW ,olleH"
 end program demo_reverse
-```
-
-### `to_string`
-
-#### Status
-
-Experimental
-
-#### Description
-
-Create a character string representing the value of the provided variable.
-
-#### Syntax
-
-`res = [[stdlib_ascii(module):to_string(interface)]] (string)`
-
-#### Class
-
-Pure function.
-
-#### Argument
-
-`val`: shall be an intrinsic integer or logical type. It is an `intent(in)` argument.
-
-#### Result value
-
-The result is an intrinsic character type.
-
-#### Example
-
-```fortran
-program demo_string_value
-    use stdlib_ascii, only : to_string
-    implicit none
-    print'(a)', to_string(-3) ! returns "-3"
-    print'(a)', to_string(.true.) ! returns "T"
-    print'(a)', to_string(42) ! returns "42"
-end program demo_string_value
-```
+```

doc/specs/stdlib_strings.md

@@ -538,3 +538,72 @@ program demo_count
 
 end program demo_count
 ```
+
+<!-- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -->
+### `to_string`
+
+#### Description
+
+Format or transfer a `integer/real/complex/logical` scalar as a string.  
+Input a wrong `format` that cause the internal-IO to fail, the result value is a string of `[*]`.
+
+#### Syntax
+
+`string = [[stdlib_strings(module):to_string(interface)]] (value [, format])`
+
+#### Status
+
+Experimental
+
+#### Class
+
+Pure function.
+
+#### Argument
+
+- `value`: Shall be an `integer/real/complex/logical` scalar.
+  This is an `intent(in)` argument.
+- `format`: Shall be a `character(len=*)` scalar like `'(F6.2)'` or just `'F6.2'`.
+  This is an `intent(in)` and `optional` argument.  
+  Contains the edit descriptor to format `value` into a string, for example `'(F6.2)'` or `'(f6.2)'`. 
+  `to_string` will automatically enclose `format` in a set of parentheses, so passing `F6.2` or `f6.2` as `format` is possible as well.
+
+#### Result value
+
+The result is an `allocatable` length `character` scalar with up to `128` cached `character` length.
+
+#### Example
+
+```fortran
+program demo_to_string
+    use stdlib_strings, only: to_string
+
+    !> Example for `complex` type
+    print *, to_string((1, 1))              !! "(1.00000000,1.00000000)"
+    print *, to_string((1, 1), '(F6.2)')    !! "(  1.00,  1.00)"
+    print *, to_string((1000, 1), '(ES0.2)'), to_string((1000, 1), '(SP,F6.3)')     
+                    !! "(1.00E+3,1.00)""(******,+1.000)"
+                    !! Too narrow formatter for real number
+                    !! Normal demonstration(`******` from Fortran Standard)
+
+    !> Example for `integer` type
+    print *, to_string(-3)                  !! "-3"
+    print *, to_string(42, '(I4)')          !! "  42"
+    print *, to_string(1, '(I0.4)'), to_string(2, '(B4)')           !! "0001""  10"  
+
+    !> Example for `real` type
+    print *, to_string(1.)                  !! "1.00000000"
+    print *, to_string(1., '(F6.2)')        !! "  1.00" 
+    print *, to_string(1., 'F6.2')          !! "  1.00" 
+    print *, to_string(1., '(SP,ES9.2)'), to_string(1, '(F7.3)')    !! "+1.00E+00""[*]"
+                    !! 1 wrong demonstration (`[*]` from `to_string`)
+
+    !> Example for `logical` type
+    print *, to_string(.true.)              !! "T"
+    print *, to_string(.true., '(L2)')      !! " T"
+    print *, to_string(.true., 'L2')        !! " T"
+    print *, to_string(.false., '(I5)')     !! "[*]"
+                    !! 1 wrong demonstrations(`[*]` from `to_string`)
+
+end program demo_to_string
+```

src/CMakeLists.txt

@@ -34,6 +34,9 @@ set(fppFiles
     stdlib_math_logspace.fypp
     stdlib_math_arange.fypp
     stdlib_string_type.fypp
+    stdlib_string_type_constructor.fypp
+    stdlib_strings_to_string.fypp
+    stdlib_strings.fypp
 )
 
 
@@ -52,7 +55,6 @@ set(SRC
     stdlib_error.f90
     stdlib_kinds.f90
     stdlib_logger.f90
-    stdlib_strings.f90
     stdlib_system.F90
     stdlib_specialfunctions.f90
     stdlib_specialfunctions_legendre.f90

src/Makefile.manual

@@ -1,4 +1,4 @@
-SRCFYPP =\
+SRCFYPP = \
         stdlib_ascii.fypp \
         stdlib_bitsets_64.fypp \
         stdlib_bitsets_large.fypp \
@@ -27,10 +27,13 @@ SRCFYPP =\
         stdlib_stats_moment_scalar.fypp \
         stdlib_stats_var.fypp \
         stdlib_math.fypp \
-		stdlib_math_linspace.fypp \
-		stdlib_math_logspace.fypp \
+	stdlib_math_linspace.fypp \
+	stdlib_math_logspace.fypp \
         stdlib_stats_distribution_PRNG.fypp \
-        stdlib_string_type.fypp
+        stdlib_string_type.fypp \
+        stdlib_string_type_constructor.fypp \
+        stdlib_strings.fypp \
+        stdlib_strings_to_string.fypp
 
 SRC = f18estop.f90 \
       stdlib_error.f90 \
@@ -40,7 +43,6 @@ SRC = f18estop.f90 \
       stdlib_kinds.f90 \
       stdlib_logger.f90 \
       stdlib_quadrature_gauss.f90 \
-      stdlib_strings.f90 \
       $(SRCGEN)
 
 LIB = libstdlib.a
@@ -77,85 +79,89 @@ stdlib_error.o: stdlib_optval.o
 stdlib_specialfunctions.o: stdlib_kinds.o
 stdlib_specialfunctions_legendre.o: stdlib_kinds.o stdlib_specialfunctions.o
 stdlib_io.o: \
-	stdlib_ascii.o \
-	stdlib_error.o \
-	stdlib_optval.o \
-	stdlib_kinds.o
+    stdlib_ascii.o \
+    stdlib_error.o \
+    stdlib_optval.o \
+    stdlib_kinds.o \
+    stdlib_ascii.o
 stdlib_linalg.o: \
-	stdlib_kinds.o
+    stdlib_kinds.o
 stdlib_linalg_diag.o: \
-	stdlib_linalg.o \
-	stdlib_kinds.o
+    stdlib_linalg.o \
+    stdlib_kinds.o
 stdlib_logger.o: stdlib_ascii.o stdlib_optval.o
 stdlib_optval.o: stdlib_kinds.o
 stdlib_quadrature.o: stdlib_kinds.o
-
 stdlib_quadrature_gauss.o: stdlib_kinds.o stdlib_quadrature.o
-
 stdlib_quadrature_simps.o: \
-	stdlib_quadrature.o \
-	stdlib_error.o \
-	stdlib_kinds.o
+    stdlib_quadrature.o \
+    stdlib_error.o \
+    stdlib_kinds.o
 stdlib_quadrature_trapz.o: \
-	stdlib_quadrature.o \
-	stdlib_error.o \
-	stdlib_kinds.o
+    stdlib_quadrature.o \
+    stdlib_error.o \
+    stdlib_kinds.o
 stdlib_sorting.o: \
-	stdlib_kinds.o \
-	stdlib_string_type.o
+    stdlib_kinds.o \
+    stdlib_string_type.o
 stdlib_sorting_ord_sort.o: \
-	stdlib_sorting.o
+    stdlib_sorting.o
 stdlib_sorting_sort.o: \
-	stdlib_sorting.o
+    stdlib_sorting.o
 stdlib_sorting_sort_index.o: \
-	stdlib_sorting.o
+    stdlib_sorting.o
 stdlib_stats.o: \
-	stdlib_kinds.o
+    stdlib_kinds.o
 stdlib_stats_corr.o: \
-	stdlib_optval.o \
-	stdlib_kinds.o \
-	stdlib_stats.o
+    stdlib_optval.o \
+    stdlib_kinds.o \
+    stdlib_stats.o
 stdlib_stats_cov.o: \
-	stdlib_optval.o \
-	stdlib_kinds.o \
-	stdlib_stats.o
+    stdlib_optval.o \
+    stdlib_kinds.o \
+    stdlib_stats.o
 stdlib_stats_mean.o: \
-	stdlib_optval.o \
-	stdlib_kinds.o \
-	stdlib_stats.o
+    stdlib_optval.o \
+    stdlib_kinds.o \
+    stdlib_stats.o
 stdlib_stats_median.o: \
-	stdlib_optval.o \
-	stdlib_kinds.o \
-	stdlib_sorting.o \
-	stdlib_stats.o
+    stdlib_optval.o \
+    stdlib_kinds.o \
+    stdlib_sorting.o \
+    stdlib_stats.o
 stdlib_stats_moment.o: \
-	stdlib_optval.o \
-	stdlib_kinds.o \
-	stdlib_stats.o
+    stdlib_optval.o \
+    stdlib_kinds.o \
+    stdlib_stats.o
 stdlib_stats_moment_all.o: \
-	stdlib_stats_moment.o
+    stdlib_stats_moment.o
 stdlib_stats_moment_mask.o: \
-	stdlib_stats_moment.o
+    stdlib_stats_moment.o
 stdlib_stats_moment_scalar.o: \
-	stdlib_stats_moment.o
+    stdlib_stats_moment.o
 stdlib_stats_var.o: \
-	stdlib_optval.o \
-	stdlib_kinds.o \
-	stdlib_stats.o
+    stdlib_optval.o \
+    stdlib_kinds.o \
+    stdlib_stats.o
 stdlib_stats_distribution_PRNG.o: \
-        stdlib_kinds.o \
-	stdlib_error.o
+    stdlib_kinds.o \
+    stdlib_error.o
 stdlib_string_type.o: stdlib_ascii.o \
     stdlib_kinds.o
+stdlib_string_type_constructor.o: stdlib_string_type.o \
+    stdlib_strings_to_string.o \
+    stdlib_strings.o
 stdlib_strings.o: stdlib_ascii.o \
     stdlib_string_type.o \
-	stdlib_optval.o
+    stdlib_optval.o \
+    stdlib_kinds.o
+stdlib_strings_to_string.o: stdlib_strings.o
 stdlib_math.o: stdlib_kinds.o \
     stdlib_optval.o
 stdlib_math_linspace.o: \
-	stdlib_math.o
+    stdlib_math.o
 stdlib_math_logspace.o: \
-	stdlib_math_linspace.o
+    stdlib_math_linspace.o
 stdlib_math_arange.o: \
     stdlib_math.o
 stdlib_linalg_outer_product.o: stdlib_linalg.o

src/stdlib_ascii.fypp

@@ -20,19 +20,6 @@ module stdlib_ascii
 
     ! Character conversion functions
     public :: to_lower, to_upper, to_title, to_sentence, reverse
-    public :: to_string
-
-    !> Version: experimental
-    !>
-    !> Create a character string representing the value of the provided variable.
-    interface to_string
-    #:for kind in INT_KINDS
-        module procedure :: to_string_integer_${kind}$
-    #:endfor
-    #:for kind in LOG_KINDS
-        module procedure :: to_string_logical_${kind}$
-    #:endfor
-    end interface to_string
 
     ! All control characters in the ASCII table (see www.asciitable.com).
     character(len=1), public, parameter :: NUL = achar(int(z'00')) !! Null
@@ -362,51 +349,4 @@ contains
 
     end function reverse
 
-    #:for kind in INT_KINDS
-    !> Represent an integer of kind ${kind}$ as character sequence
-    pure function to_string_integer_${kind}$(val) result(string)
-        integer, parameter :: ik = ${kind}$
-        integer(ik), intent(in) :: val
-        character(len=:), allocatable :: string
-        integer, parameter :: buffer_len = range(val)+2
-        character(len=buffer_len) :: buffer
-        integer :: pos
-        integer(ik) :: n
-        character(len=1), parameter :: numbers(0:9) = &
-            ["0", "1", "2", "3", "4", "5", "6", "7", "8", "9"]
-
-        if (val == 0_ik) then
-            string = numbers(0)
-            return
-        end if
-
-        n = abs(val)
-        buffer = ""
-
-        pos = buffer_len + 1
-        do while (n > 0_ik)
-            pos = pos - 1
-            buffer(pos:pos) = numbers(mod(n, 10_ik))
-            n = n/10_ik
-        end do
-        if (val < 0_ik) then
-            pos = pos - 1
-            buffer(pos:pos) = '-'
-        end if
-
-        string = buffer(pos:)
-    end function to_string_integer_${kind}$
-    #:endfor
-
-    #:for kind in LOG_KINDS
-    !> Represent an logical of kind ${kind}$ as character sequence
-    pure function to_string_logical_${kind}$(val) result(string)
-        integer, parameter :: ik = ${kind}$
-        logical(ik), intent(in) :: val
-        character(len=1) :: string
-
-        string = merge("T", "F", val)
-    end function to_string_logical_${kind}$
-    #:endfor
-
 end module stdlib_ascii