diff --git a/Makefile b/Makefile
index 1462dbe..3c0129a 100644
--- a/Makefile
+++ b/Makefile
@@ -1,7 +1,7 @@
 all: proto grammar y2j
 
 grammar:
-	flexgo -G -v -o lexer.go lexer.l && goyacc -p yr -o parser.go grammar.y
+	flexgo -G -v -o parser/lexer.go parser/lexer.l && goyacc -p yr -o parser/parser.go parser/grammar.y
 
 hexgrammar:
 	flexgo -G -v -o hex/hex_lexer.go hex/hex_lexer.l && goyacc -p xx -o hex/hex_parser.go hex/hex_grammar.y
@@ -21,4 +21,4 @@ release: parser lexer
 	GOOS=windows go build -o y2j.exe github.com/VirusTotal/gyp/cmd/y2j
 
 clean:
-	rm lexer.go parser.go yara.pb.go y.output y2j j2y
+	rm parser/lexer.go parser/parser.go pb/yara.pb.go y.output y2j j2y
diff --git a/adapter.go b/adapter.go
deleted file mode 100644
index 9328f5d..0000000
--- a/adapter.go
+++ /dev/null
@@ -1,105 +0,0 @@
-// adapter.go provides an adapter for a flexgo lexer to work
-// with a goyacc parser
-
-package gyp
-
-import (
-	"bytes"
-	"fmt"
-	"io"
-	"io/ioutil"
-
-	"github.com/VirusTotal/gyp/ast"
-	gyperror "github.com/VirusTotal/gyp/error"
-)
-
-func init() {
-	yrErrorVerbose = true
-}
-
-// Parse parses a YARA rule from the provided input source.
-func Parse(input io.Reader) (rs *ast.RuleSet, err error) {
-	defer func() {
-		if r := recover(); r != nil {
-			if yaraError, ok := r.(gyperror.Error); ok {
-				err = yaraError
-			} else {
-				err = gyperror.Error{
-					Code:    gyperror.UnknownError,
-					Message: fmt.Sprintf("%v", r),
-				}
-			}
-		}
-	}()
-
-	lexer := &lexer{
-		scanner: *NewScanner(),
-		ruleSet: &ast.RuleSet{
-			Imports: make([]string, 0),
-			Rules:   make([]*ast.Rule, 0),
-		},
-	}
-	lexer.scanner.In = input
-	lexer.scanner.Out = ioutil.Discard
-
-	if result := yrParse(lexer); result != 0 {
-		err = lexer.err
-	}
-
-	return lexer.ruleSet, err
-}
-
-// ParseString parses a YARA rule from the provided string.
-func ParseString(s string) (*ast.RuleSet, error) {
-	return Parse(bytes.NewBufferString(s))
-}
-
-// Lexer is an adapter that fits the flexgo lexer ("Scanner") into goyacc
-type lexer struct {
-	scanner Scanner
-	err     gyperror.Error
-	ruleSet *ast.RuleSet
-}
-
-// Lex provides the interface expected by the goyacc parser.
-// It sets the context's lval pointer (defined in the lexer file)
-// to the one passed as an argument so that the parser actions
-// can make use of it.
-func (l *lexer) Lex(lval *yrSymType) int {
-	l.scanner.Context.lval = lval
-	r := l.scanner.Lex()
-	if r.Error.Code != 0 {
-		r.Error.Line = l.scanner.Lineno
-		panic(r.Error)
-	}
-	return r.Token
-}
-
-// Error satisfies the interface expected of the goyacc parser.
-func (l *lexer) Error(msg string) {
-	l.err = gyperror.Error{
-		Code:    gyperror.LexicalError,
-		Line:    l.scanner.Lineno,
-		Message: msg,
-	}
-}
-
-// SetError sets the lexer error. The error message can be built by passing
-// a format string and arguments as fmt.Sprintf. This function returns 1 as
-// it's intended to by used in grammar.y as:
-//   return lexer.SetError(...)
-// By returning 1 from the parser the parsing is aborted.
-func (l *lexer) SetError(code gyperror.Code, format string, a ...interface{}) int {
-	l.err = gyperror.Error{
-		Code:    code,
-		Line:    l.scanner.Lineno,
-		Message: fmt.Sprintf(format, a...),
-	}
-	return 1
-}
-
-// Helper function that casts a yrLexer interface to a lexer struct. This
-// function is used in grammar.y.
-func asLexer(l yrLexer) *lexer {
-	return l.(*lexer)
-}
diff --git a/gyp.go b/gyp.go
new file mode 100644
index 0000000..51b8ad3
--- /dev/null
+++ b/gyp.go
@@ -0,0 +1,36 @@
+/*
+Package gyp provides a pure Go parser for YARA rules.
+
+For example, you can parse YARA rules from a string:
+	ruleset, err := gyp.ParseString("rule test { condition: true }")
+
+Or from a io.Reader:
+	ruleset, err := gyp.Parse(os.Stdin)
+
+The rules can be written to source again:
+	err := ruleset.WriteSource(os.Stdout)
+
+Or you can iterate over the rules and inspect their attributes:
+	for _, rule := ruleset.Rules {
+		fmt.Println(rule.Identifier)
+	}
+*/
+package gyp
+
+import (
+	"bytes"
+	"io"
+
+	"github.com/VirusTotal/gyp/ast"
+	"github.com/VirusTotal/gyp/parser"
+)
+
+// Parse parses a YARA rule from the provided input source.
+func Parse(input io.Reader) (rs *ast.RuleSet, err error) {
+	return parser.Parse(input)
+}
+
+// ParseString parses a YARA rule from the provided string.
+func ParseString(s string) (*ast.RuleSet, error) {
+	return Parse(bytes.NewBufferString(s))
+}
diff --git a/parser_test.go b/gyp_test.go
similarity index 100%
rename from parser_test.go
rename to gyp_test.go
diff --git a/grammar.y b/parser/grammar.y
similarity index 90%
rename from grammar.y
rename to parser/grammar.y
index 8075e15..f1c87cd 100644
--- a/grammar.y
+++ b/parser/grammar.y
@@ -28,9 +28,12 @@ SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
 
 %{
-package gyp
+package parser
 
 import (
+    "fmt"
+    "io"
+    "io/ioutil"
     "strings"
     "github.com/VirusTotal/gyp/ast"
     gyperror "github.com/VirusTotal/gyp/error"
@@ -55,6 +58,93 @@ type stringModifiers struct {
   XorMax int32
 }
 
+// Lexer is an adapter that fits the flexgo lexer ("Scanner") into goyacc
+type lexer struct {
+	scanner Scanner
+	err     gyperror.Error
+	ruleSet *ast.RuleSet
+}
+
+// Lex provides the interface expected by the goyacc parser.
+// It sets the context's lval pointer (defined in the lexer file)
+// to the one passed as an argument so that the parser actions
+// can make use of it.
+func (l *lexer) Lex(lval *yrSymType) int {
+	l.scanner.Context.lval = lval
+	r := l.scanner.Lex()
+	if r.Error.Code != 0 {
+		r.Error.Line = l.scanner.Lineno
+		panic(r.Error)
+	}
+	return r.Token
+}
+
+// Error satisfies the interface expected of the goyacc parser.
+func (l *lexer) Error(msg string) {
+	l.err = gyperror.Error{
+		Code:    gyperror.LexicalError,
+		Line:    l.scanner.Lineno,
+		Message: msg,
+	}
+}
+
+// setError sets the lexer error. The error message can be built by passing
+// a format string and arguments as fmt.Sprintf. This function returns 1 as
+// it's intended to be used by Parse as:
+//   return lexer.setError(...)
+// By returning 1 from Parse the parsing is aborted.
+func (l *lexer) setError(code gyperror.Code, format string, a ...interface{}) int {
+	l.err = gyperror.Error{
+		Code:    code,
+		Line:    l.scanner.Lineno,
+		Message: fmt.Sprintf(format, a...),
+	}
+	return 1
+}
+
+
+// Helper function that casts a yrLexer interface to a lexer struct.
+func asLexer(l yrLexer) *lexer {
+	return l.(*lexer)
+}
+
+
+func Parse(input io.Reader) (rs *ast.RuleSet, err error) {
+	defer func() {
+		if r := recover(); r != nil {
+			if yaraError, ok := r.(gyperror.Error); ok {
+				err = yaraError
+			} else {
+				err = gyperror.Error{
+					Code:    gyperror.UnknownError,
+					Message: fmt.Sprintf("%v", r),
+				}
+			}
+		}
+	}()
+
+	lexer := &lexer{
+		scanner: *NewScanner(),
+		ruleSet: &ast.RuleSet{
+			Imports: make([]string, 0),
+			Rules:   make([]*ast.Rule, 0),
+		},
+	}
+	lexer.scanner.In = input
+	lexer.scanner.Out = ioutil.Discard
+
+	if result := yrParse(lexer); result != 0 {
+		err = lexer.err
+	}
+
+	return lexer.ruleSet, err
+}
+
+
+func init() {
+	yrErrorVerbose = true
+}
+
 
 %}
 
@@ -225,7 +315,7 @@ rule
         // Forbid duplicate rules
         for _, r := range lexer.ruleSet.Rules {
             if $3 == r.Identifier {
-              return lexer.SetError(
+              return lexer.setError(
                 gyperror.DuplicateRuleError, `duplicate rule "%s"`, $3)
             }
         }
@@ -329,7 +419,7 @@ tag_list
 
         for _, tag := range $1 {
           if tag == $2 {
-            return lexer.SetError(
+            return lexer.setError(
                 gyperror.DuplicateTagError, `duplicate tag "%s"`, $2)
           }
         }
@@ -449,7 +539,7 @@ string_modifiers
     | string_modifiers string_modifier
       {
         if $1.modifiers & $2.modifiers != 0 {
-          return asLexer(yrlex).SetError(
+          return asLexer(yrlex).setError(
             gyperror.DuplicateModifierError, `duplicate modifier`)
         }
 
@@ -492,19 +582,19 @@ string_modifier
         lexer := asLexer(yrlex)
 
         if $3 < 0 {
-          return lexer.SetError(
+          return lexer.setError(
             gyperror.InvalidStringModifierError,
             "lower bound for xor range exceeded (min: 0)")
         }
 
         if $5 > 255 {
-          return lexer.SetError(
+          return lexer.setError(
             gyperror.InvalidStringModifierError,
             "upper bound for xor range exceeded (max: 255)")
         }
 
         if $3 > $5 {
-          return lexer.SetError(
+          return lexer.setError(
             gyperror.InvalidStringModifierError,
             "xor lower bound exceeds upper bound")
         }
diff --git a/lexer.go b/parser/lexer.go
similarity index 95%
rename from lexer.go
rename to parser/lexer.go
index b74b1d8..4b451c2 100644
--- a/lexer.go
+++ b/parser/lexer.go
@@ -1,6 +1,6 @@
-//line lexer.go:2
-//line lexer.l:33
-package gyp
+//line parser/lexer.go:2
+//line parser/lexer.l:33
+package parser
 
 import (
     "fmt"
@@ -51,7 +51,7 @@ type YYcontext struct {
 
 
 
-//line lexer.go:55
+//line parser/lexer.go:55
 
 // START OF SKELL ------------------------------------------------------
 // A lexical scanner generated by flexgo
@@ -452,7 +452,7 @@ var yyRuleCanMatchEol = [74]int32{   0,
     0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 
     0, 1, 1, 0, 0, 0, 0, 1, 0, 0, 1, 1, 0, 0,     };
 
-//line lexer.l:1
+//line parser/lexer.l:1
 /*
 Copyright (c) 2007-2013. The YARA Authors. All Rights Reserved.
 
@@ -483,7 +483,7 @@ SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
 /* Lexical analyzer for YARA */
 
-//line lexer.l:84
+//line parser/lexer.l:84
 
  
 
@@ -495,7 +495,7 @@ const eof = 0
 
 
 
-//line lexer.go:499
+//line parser/lexer.go:499
 // SKEL ----------------------------------------------------------------
 
 const yyInitial  = 0
@@ -578,10 +578,10 @@ func (yy *Scanner) Lex() YYtype {
 	_ = yyout
 
 // [7.0] user's declarations go here -----------------------------------
-//line lexer.l:124
+//line parser/lexer.l:124
 
 
-//line lexer.go:585
+//line parser/lexer.go:585
 // SKEL ----------------------------------------------------------------
 
 	for { // loops until end-of-file is reached
@@ -680,7 +680,7 @@ case 1:
     text = append(text, yytext...)
   }
 
-//line lexer.l:126
+//line parser/lexer.l:126
 { return Token(_DOT_DOT_);     }
 case 2:
 
@@ -692,7 +692,7 @@ case 2:
   }
 
 
-//line lexer.l:127
+//line parser/lexer.l:127
 { return Token(_LT_);          }
 case 3:
 
@@ -704,7 +704,7 @@ case 3:
   }
 
 
-//line lexer.l:128
+//line parser/lexer.l:128
 { return Token(_GT_);          }
 case 4:
 
@@ -716,7 +716,7 @@ case 4:
   }
 
 
-//line lexer.l:129
+//line parser/lexer.l:129
 { return Token(_LE_);          }
 case 5:
 
@@ -728,7 +728,7 @@ case 5:
   }
 
 
-//line lexer.l:130
+//line parser/lexer.l:130
 { return Token(_GE_);          }
 case 6:
 
@@ -740,7 +740,7 @@ case 6:
   }
 
 
-//line lexer.l:131
+//line parser/lexer.l:131
 { return Token(_EQ_);          }
 case 7:
 
@@ -752,7 +752,7 @@ case 7:
   }
 
 
-//line lexer.l:132
+//line parser/lexer.l:132
 { return Token(_NEQ_);         }
 case 8:
 
@@ -764,7 +764,7 @@ case 8:
   }
 
 
-//line lexer.l:133
+//line parser/lexer.l:133
 { return Token(_SHIFT_LEFT_);  }
 case 9:
 
@@ -776,7 +776,7 @@ case 9:
   }
 
 
-//line lexer.l:134
+//line parser/lexer.l:134
 { return Token(_SHIFT_RIGHT_); }
 case 10:
 
@@ -788,7 +788,7 @@ case 10:
   }
 
 
-//line lexer.l:135
+//line parser/lexer.l:135
 { return Token(_PRIVATE_);     }
 case 11:
 
@@ -800,7 +800,7 @@ case 11:
   }
 
 
-//line lexer.l:136
+//line parser/lexer.l:136
 { return Token(_GLOBAL_);      }
 case 12:
 
@@ -812,7 +812,7 @@ case 12:
   }
 
 
-//line lexer.l:137
+//line parser/lexer.l:137
 { return Token(_RULE_);        }
 case 13:
 
@@ -824,7 +824,7 @@ case 13:
   }
 
 
-//line lexer.l:138
+//line parser/lexer.l:138
 { return Token(_META_);        }
 case 14:
 
@@ -836,7 +836,7 @@ case 14:
   }
 
 
-//line lexer.l:139
+//line parser/lexer.l:139
 { return Token(_STRINGS_);     }
 case 15:
 
@@ -848,7 +848,7 @@ case 15:
   }
 
 
-//line lexer.l:140
+//line parser/lexer.l:140
 { return Token(_ASCII_);       }
 case 16:
 
@@ -860,7 +860,7 @@ case 16:
   }
 
 
-//line lexer.l:141
+//line parser/lexer.l:141
 { return Token(_WIDE_);        }
 case 17:
 
@@ -872,7 +872,7 @@ case 17:
   }
 
 
-//line lexer.l:142
+//line parser/lexer.l:142
 { return Token(_XOR_);         }
 case 18:
 
@@ -884,7 +884,7 @@ case 18:
   }
 
 
-//line lexer.l:143
+//line parser/lexer.l:143
 { return Token(_FULLWORD_);    }
 case 19:
 
@@ -896,7 +896,7 @@ case 19:
   }
 
 
-//line lexer.l:144
+//line parser/lexer.l:144
 { return Token(_NOCASE_);      }
 case 20:
 
@@ -908,7 +908,7 @@ case 20:
   }
 
 
-//line lexer.l:145
+//line parser/lexer.l:145
 { return Token(_CONDITION_);   }
 case 21:
 
@@ -920,7 +920,7 @@ case 21:
   }
 
 
-//line lexer.l:146
+//line parser/lexer.l:146
 { return Token(_TRUE_);        }
 case 22:
 
@@ -932,7 +932,7 @@ case 22:
   }
 
 
-//line lexer.l:147
+//line parser/lexer.l:147
 { return Token(_FALSE_);       }
 case 23:
 
@@ -944,7 +944,7 @@ case 23:
   }
 
 
-//line lexer.l:148
+//line parser/lexer.l:148
 { return Token(_NOT_);         }
 case 24:
 
@@ -956,7 +956,7 @@ case 24:
   }
 
 
-//line lexer.l:149
+//line parser/lexer.l:149
 { return Token(_AND_);         }
 case 25:
 
@@ -968,7 +968,7 @@ case 25:
   }
 
 
-//line lexer.l:150
+//line parser/lexer.l:150
 { return Token(_OR_);          }
 case 26:
 
@@ -980,7 +980,7 @@ case 26:
   }
 
 
-//line lexer.l:151
+//line parser/lexer.l:151
 { return Token(_AT_);          }
 case 27:
 
@@ -992,7 +992,7 @@ case 27:
   }
 
 
-//line lexer.l:152
+//line parser/lexer.l:152
 { return Token(_IN_);          }
 case 28:
 
@@ -1004,7 +1004,7 @@ case 28:
   }
 
 
-//line lexer.l:153
+//line parser/lexer.l:153
 { return Token(_OF_);          }
 case 29:
 
@@ -1016,7 +1016,7 @@ case 29:
   }
 
 
-//line lexer.l:154
+//line parser/lexer.l:154
 { return Token(_THEM_);        }
 case 30:
 
@@ -1028,7 +1028,7 @@ case 30:
   }
 
 
-//line lexer.l:155
+//line parser/lexer.l:155
 { return Token(_FOR_);         }
 case 31:
 
@@ -1040,7 +1040,7 @@ case 31:
   }
 
 
-//line lexer.l:156
+//line parser/lexer.l:156
 { return Token(_ALL_);         }
 case 32:
 
@@ -1052,7 +1052,7 @@ case 32:
   }
 
 
-//line lexer.l:157
+//line parser/lexer.l:157
 { return Token(_ANY_);         }
 case 33:
 
@@ -1064,7 +1064,7 @@ case 33:
   }
 
 
-//line lexer.l:158
+//line parser/lexer.l:158
 { return Token(_ENTRYPOINT_);  }
 case 34:
 
@@ -1076,7 +1076,7 @@ case 34:
   }
 
 
-//line lexer.l:159
+//line parser/lexer.l:159
 { return Token(_FILESIZE_);    }
 case 35:
 
@@ -1088,7 +1088,7 @@ case 35:
   }
 
 
-//line lexer.l:160
+//line parser/lexer.l:160
 { return Token(_MATCHES_);     }
 case 36:
 
@@ -1100,7 +1100,7 @@ case 36:
   }
 
 
-//line lexer.l:161
+//line parser/lexer.l:161
 { return Token(_CONTAINS_);    }
 case 37:
 
@@ -1112,7 +1112,7 @@ case 37:
   }
 
 
-//line lexer.l:162
+//line parser/lexer.l:162
 { return Token(_IMPORT_);      }
 case 38:
 
@@ -1124,7 +1124,7 @@ case 38:
   }
 
 
-//line lexer.l:163
+//line parser/lexer.l:163
 { return Token(_INCLUDE_);     }
 case 39:
 
@@ -1136,7 +1136,7 @@ case 39:
   }
 
 
-//line lexer.l:165
+//line parser/lexer.l:165
 { yy.start = 1 + 2*  (comment);       }
 case 40:
 
@@ -1148,7 +1148,7 @@ case 40:
   }
 
 
-//line lexer.l:166
+//line parser/lexer.l:166
 { yy.start = 1 + 2*  (yyInitial );       }
 case 41:
 /* rule 41 can match eol */
@@ -1161,7 +1161,7 @@ case 41:
   }
 
 
-//line lexer.l:167
+//line parser/lexer.l:167
 { /* skip comments */   }
 case 42:
 
@@ -1173,7 +1173,7 @@ case 42:
   }
 
 
-//line lexer.l:170
+//line parser/lexer.l:170
 { /* skip single-line comments */ }
 case (yyEndOfBuffer + yyInitial  + 1) :
 	fallthrough
@@ -1184,7 +1184,7 @@ case (yyEndOfBuffer + regexp + 1) :
 case (yyEndOfBuffer + include + 1) :
 	fallthrough
 case (yyEndOfBuffer + comment + 1) :
-//line lexer.l:172
+//line parser/lexer.l:172
 { return Token(eof) }
 case 43:
 
@@ -1196,7 +1196,7 @@ case 43:
   }
 
 
-//line lexer.l:175
+//line parser/lexer.l:175
 {
   yy.Context.lval.s = string(yytext)
   return Token(_STRING_IDENTIFIER_WITH_WILDCARD_);
@@ -1211,7 +1211,7 @@ case 44:
   }
 
 
-//line lexer.l:181
+//line parser/lexer.l:181
 {
   yy.Context.lval.s = string(yytext)
   return Token(_STRING_IDENTIFIER_);
@@ -1226,7 +1226,7 @@ case 45:
   }
 
 
-//line lexer.l:187
+//line parser/lexer.l:187
 {
   yy.Context.lval.s = string(yytext)
   return Token(_STRING_COUNT_);
@@ -1241,7 +1241,7 @@ case 46:
   }
 
 
-//line lexer.l:193
+//line parser/lexer.l:193
 {
   yy.Context.lval.s = string(yytext)
   return Token(_STRING_OFFSET_);
@@ -1256,7 +1256,7 @@ case 47:
   }
 
 
-//line lexer.l:199
+//line parser/lexer.l:199
 {
   yy.Context.lval.s = string(yytext)
   return Token(_STRING_LENGTH_);
@@ -1271,7 +1271,7 @@ case 48:
   }
 
 
-//line lexer.l:205
+//line parser/lexer.l:205
 {
   yy.Context.lval.s = string(yytext)
   return Token(_INTEGER_FUNCTION_);
@@ -1286,7 +1286,7 @@ case 49:
   }
 
 
-//line lexer.l:211
+//line parser/lexer.l:211
 {
   yy.Context.lval.s = string(yytext)
   return Token(_IDENTIFIER_);
@@ -1301,7 +1301,7 @@ case 50:
   }
 
 
-//line lexer.l:217
+//line parser/lexer.l:217
 {
   var err error
   s := strings.TrimRight(YYtext, "MKB")
@@ -1341,7 +1341,7 @@ case 51:
   }
 
 
-//line lexer.l:247
+//line parser/lexer.l:247
 {
   return Token(_DOUBLE_);
 }
@@ -1355,7 +1355,7 @@ case 52:
   }
 
 
-//line lexer.l:251
+//line parser/lexer.l:251
 {
   var err error
   yy.Context.lval.i64, err = strconv.ParseInt(YYtext, 0, 64)
@@ -1377,7 +1377,7 @@ case 53:
   }
 
 
-//line lexer.l:263
+//line parser/lexer.l:263
 {
   var err error
   s := strings.TrimLeft(YYtext, "0o")
@@ -1399,7 +1399,7 @@ case 54:
   }
 
 
-//line lexer.l:276
+//line parser/lexer.l:276
 {     /* saw closing quote - all done */
 
   // NOTE: text will end with `"` char
@@ -1420,7 +1420,7 @@ case 55:
   }
 
 
-//line lexer.l:288
+//line parser/lexer.l:288
 {
 }
 case 56:
@@ -1433,7 +1433,7 @@ case 56:
   }
 
 
-//line lexer.l:292
+//line parser/lexer.l:292
 {
 }
 case 57:
@@ -1446,7 +1446,7 @@ case 57:
   }
 
 
-//line lexer.l:296
+//line parser/lexer.l:296
 {
 }
 case 58:
@@ -1459,7 +1459,7 @@ case 58:
   }
 
 
-//line lexer.l:300
+//line parser/lexer.l:300
 {
 }
 case 59:
@@ -1472,7 +1472,7 @@ case 59:
   }
 
 
-//line lexer.l:304
+//line parser/lexer.l:304
 {
 }
 case 60:
@@ -1485,7 +1485,7 @@ case 60:
   }
 
 
-//line lexer.l:308
+//line parser/lexer.l:308
 { }
 case 61:
 /* rule 61 can match eol */
@@ -1498,7 +1498,7 @@ case 61:
   }
 
 
-//line lexer.l:311
+//line parser/lexer.l:311
 {
   return Error(
     gyperror.UnterminatedStringError,
@@ -1515,7 +1515,7 @@ case 62:
   }
 
 
-//line lexer.l:318
+//line parser/lexer.l:318
 {
   return Error(
     gyperror.IllegalEscapeSequenceError,
@@ -1531,7 +1531,7 @@ case 63:
   }
 
 
-//line lexer.l:325
+//line parser/lexer.l:325
 {
 
   collectText = false
@@ -1573,7 +1573,7 @@ case 64:
   }
 
 
-//line lexer.l:358
+//line parser/lexer.l:358
 {
 }
 case 65:
@@ -1586,7 +1586,7 @@ case 65:
   }
 
 
-//line lexer.l:362
+//line parser/lexer.l:362
 {
 }
 case 66:
@@ -1599,7 +1599,7 @@ case 66:
   }
 
 
-//line lexer.l:366
+//line parser/lexer.l:366
 { }
 case 67:
 /* rule 67 can match eol */
@@ -1612,7 +1612,7 @@ case 67:
   }
 
 
-//line lexer.l:369
+//line parser/lexer.l:369
 {
   return Error(
     gyperror.UnterminatedRegexError,
@@ -1628,7 +1628,7 @@ case 68:
   }
 
 
-//line lexer.l:376
+//line parser/lexer.l:376
 {
   collectText = true
   text = []byte{}
@@ -1644,7 +1644,7 @@ case 69:
   }
 
 
-//line lexer.l:383
+//line parser/lexer.l:383
 {
   collectText = true
   text = []byte{}
@@ -1661,7 +1661,7 @@ case 70:
   }
 
 
-//line lexer.l:390
+//line parser/lexer.l:390
 {
   // Match hex-digits with whitespace or comments. The latter are stripped
   // out by hex_lexer.l
@@ -1690,7 +1690,7 @@ case 71:
   }
 
 
-//line lexer.l:409
+//line parser/lexer.l:409
 /* skip whitespace */
 case 72:
 
@@ -1702,7 +1702,7 @@ case 72:
   }
 
 
-//line lexer.l:411
+//line parser/lexer.l:411
 {
 
   r := int(yytext[0])
@@ -1725,9 +1725,9 @@ case 73:
   }
 
 
-//line lexer.l:424
+//line parser/lexer.l:424
 yyout.Write(yytext) 
-//line lexer.go:1731
+//line parser/lexer.go:1731
 // SKEL ----------------------------------------------------------------
 
 		case yyEndOfBuffer:
@@ -2188,7 +2188,7 @@ func YYmain(filenames ...string) (interface{}, error) {
 }
 
 // END OF SKELL --------------------------------------------------------
-//line lexer.l:424
+//line parser/lexer.l:424
 
 
 
diff --git a/lexer.l b/parser/lexer.l
similarity index 99%
rename from lexer.l
rename to parser/lexer.l
index 667c364..7ff0d93 100644
--- a/lexer.l
+++ b/parser/lexer.l
@@ -30,7 +30,7 @@ SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 /* Lexical analyzer for YARA */
 
 %top{
-package gyp
+package parser
 
 import (
     "fmt"
diff --git a/parser.go b/parser/parser.go
similarity index 85%
rename from parser.go
rename to parser/parser.go
index 64e4b3b..740320d 100644
--- a/parser.go
+++ b/parser/parser.go
@@ -1,14 +1,17 @@
-// Code generated by goyacc -p yr -o parser.go grammar.y. DO NOT EDIT.
+// Code generated by goyacc -p yr -o parser/parser.go parser/grammar.y. DO NOT EDIT.
 
-//line grammar.y:31
-package gyp
+//line parser/grammar.y:31
+package parser
 
 import __yyfmt__ "fmt"
 
-//line grammar.y:31
+//line parser/grammar.y:31
 import (
+	"fmt"
 	"github.com/VirusTotal/gyp/ast"
 	gyperror "github.com/VirusTotal/gyp/error"
+	"io"
+	"io/ioutil"
 	"strings"
 )
 
@@ -31,7 +34,91 @@ type stringModifiers struct {
 	XorMax int32
 }
 
-//line grammar.y:161
+// Lexer is an adapter that fits the flexgo lexer ("Scanner") into goyacc
+type lexer struct {
+	scanner Scanner
+	err     gyperror.Error
+	ruleSet *ast.RuleSet
+}
+
+// Lex provides the interface expected by the goyacc parser.
+// It sets the context's lval pointer (defined in the lexer file)
+// to the one passed as an argument so that the parser actions
+// can make use of it.
+func (l *lexer) Lex(lval *yrSymType) int {
+	l.scanner.Context.lval = lval
+	r := l.scanner.Lex()
+	if r.Error.Code != 0 {
+		r.Error.Line = l.scanner.Lineno
+		panic(r.Error)
+	}
+	return r.Token
+}
+
+// Error satisfies the interface expected of the goyacc parser.
+func (l *lexer) Error(msg string) {
+	l.err = gyperror.Error{
+		Code:    gyperror.LexicalError,
+		Line:    l.scanner.Lineno,
+		Message: msg,
+	}
+}
+
+// setError sets the lexer error. The error message can be built by passing
+// a format string and arguments as fmt.Sprintf. This function returns 1 as
+// it's intended to be used by Parse as:
+//   return lexer.setError(...)
+// By returning 1 from Parse the parsing is aborted.
+func (l *lexer) setError(code gyperror.Code, format string, a ...interface{}) int {
+	l.err = gyperror.Error{
+		Code:    code,
+		Line:    l.scanner.Lineno,
+		Message: fmt.Sprintf(format, a...),
+	}
+	return 1
+}
+
+// Helper function that casts a yrLexer interface to a lexer struct.
+func asLexer(l yrLexer) *lexer {
+	return l.(*lexer)
+}
+
+func Parse(input io.Reader) (rs *ast.RuleSet, err error) {
+	defer func() {
+		if r := recover(); r != nil {
+			if yaraError, ok := r.(gyperror.Error); ok {
+				err = yaraError
+			} else {
+				err = gyperror.Error{
+					Code:    gyperror.UnknownError,
+					Message: fmt.Sprintf("%v", r),
+				}
+			}
+		}
+	}()
+
+	lexer := &lexer{
+		scanner: *NewScanner(),
+		ruleSet: &ast.RuleSet{
+			Imports: make([]string, 0),
+			Rules:   make([]*ast.Rule, 0),
+		},
+	}
+	lexer.scanner.In = input
+	lexer.scanner.Out = ioutil.Discard
+
+	if result := yrParse(lexer); result != 0 {
+		err = lexer.err
+	}
+
+	return lexer.ruleSet, err
+}
+
+func init() {
+	yrErrorVerbose = true
+}
+
+//line parser/grammar.y:251
 type yrSymType struct {
 	yys        int
 	i64        int64
@@ -192,7 +279,7 @@ const yrEofCode = 1
 const yrErrCode = 2
 const yrInitialStackSize = 16
 
-//line grammar.y:996
+//line parser/grammar.y:1086
 
 // This function takes an operator and two operands and returns a Expression
 // representing the operation. If the left operand is an operation of the
@@ -768,47 +855,47 @@ yrdefault:
 
 	case 2:
 		yrDollar = yrS[yrpt-2 : yrpt+1]
-//line grammar.y:191
+//line parser/grammar.y:281
 		{
 			ruleSet := asLexer(yrlex).ruleSet
 			ruleSet.Rules = append(ruleSet.Rules, yrDollar[2].rule)
 		}
 	case 3:
 		yrDollar = yrS[yrpt-2 : yrpt+1]
-//line grammar.y:196
+//line parser/grammar.y:286
 		{
 			ruleSet := asLexer(yrlex).ruleSet
 			ruleSet.Imports = append(ruleSet.Imports, yrDollar[2].s)
 		}
 	case 4:
 		yrDollar = yrS[yrpt-3 : yrpt+1]
-//line grammar.y:201
+//line parser/grammar.y:291
 		{
 			ruleSet := asLexer(yrlex).ruleSet
 			ruleSet.Includes = append(ruleSet.Includes, yrDollar[3].s)
 		}
 	case 5:
 		yrDollar = yrS[yrpt-2 : yrpt+1]
-//line grammar.y:206
+//line parser/grammar.y:296
 		{
 
 		}
 	case 6:
 		yrDollar = yrS[yrpt-2 : yrpt+1]
-//line grammar.y:214
+//line parser/grammar.y:304
 		{
 			yrVAL.s = yrDollar[2].s
 		}
 	case 7:
 		yrDollar = yrS[yrpt-3 : yrpt+1]
-//line grammar.y:222
+//line parser/grammar.y:312
 		{
 			lexer := asLexer(yrlex)
 
 			// Forbid duplicate rules
 			for _, r := range lexer.ruleSet.Rules {
 				if yrDollar[3].s == r.Identifier {
-					return lexer.SetError(
+					return lexer.setError(
 						gyperror.DuplicateRuleError, `duplicate rule "%s"`, yrDollar[3].s)
 				}
 			}
@@ -821,7 +908,7 @@ yrdefault:
 		}
 	case 8:
 		yrDollar = yrS[yrpt-8 : yrpt+1]
-//line grammar.y:240
+//line parser/grammar.y:330
 		{
 			yrDollar[4].rule.Tags = yrDollar[5].ss
 			yrDollar[4].rule.Meta = yrDollar[7].metas
@@ -829,92 +916,92 @@ yrdefault:
 		}
 	case 9:
 		yrDollar = yrS[yrpt-11 : yrpt+1]
-//line grammar.y:246
+//line parser/grammar.y:336
 		{
 			yrDollar[4].rule.Condition = yrDollar[10].expr
 			yrVAL.rule = yrDollar[4].rule
 		}
 	case 10:
 		yrDollar = yrS[yrpt-0 : yrpt+1]
-//line grammar.y:255
+//line parser/grammar.y:345
 		{
 			yrVAL.metas = []*ast.Meta{}
 		}
 	case 11:
 		yrDollar = yrS[yrpt-3 : yrpt+1]
-//line grammar.y:259
+//line parser/grammar.y:349
 		{
 			yrVAL.metas = yrDollar[3].metas
 		}
 	case 12:
 		yrDollar = yrS[yrpt-0 : yrpt+1]
-//line grammar.y:267
+//line parser/grammar.y:357
 		{
 			yrVAL.yss = []ast.String{}
 		}
 	case 13:
 		yrDollar = yrS[yrpt-3 : yrpt+1]
-//line grammar.y:271
+//line parser/grammar.y:361
 		{
 			yrVAL.yss = yrDollar[3].yss
 		}
 	case 14:
 		yrDollar = yrS[yrpt-3 : yrpt+1]
-//line grammar.y:279
+//line parser/grammar.y:369
 		{
 			yrVAL.expr = yrDollar[3].expr
 		}
 	case 15:
 		yrDollar = yrS[yrpt-0 : yrpt+1]
-//line grammar.y:287
+//line parser/grammar.y:377
 		{
 			yrVAL.mod = 0
 		}
 	case 16:
 		yrDollar = yrS[yrpt-2 : yrpt+1]
-//line grammar.y:291
+//line parser/grammar.y:381
 		{
 			yrVAL.mod = yrDollar[1].mod | yrDollar[2].mod
 		}
 	case 17:
 		yrDollar = yrS[yrpt-1 : yrpt+1]
-//line grammar.y:299
+//line parser/grammar.y:389
 		{
 			yrVAL.mod = ModPrivate
 		}
 	case 18:
 		yrDollar = yrS[yrpt-1 : yrpt+1]
-//line grammar.y:303
+//line parser/grammar.y:393
 		{
 			yrVAL.mod = ModGlobal
 		}
 	case 19:
 		yrDollar = yrS[yrpt-0 : yrpt+1]
-//line grammar.y:311
+//line parser/grammar.y:401
 		{
 			yrVAL.ss = []string{}
 		}
 	case 20:
 		yrDollar = yrS[yrpt-2 : yrpt+1]
-//line grammar.y:315
+//line parser/grammar.y:405
 		{
 			yrVAL.ss = yrDollar[2].ss
 		}
 	case 21:
 		yrDollar = yrS[yrpt-1 : yrpt+1]
-//line grammar.y:323
+//line parser/grammar.y:413
 		{
 			yrVAL.ss = []string{yrDollar[1].s}
 		}
 	case 22:
 		yrDollar = yrS[yrpt-2 : yrpt+1]
-//line grammar.y:327
+//line parser/grammar.y:417
 		{
 			lexer := asLexer(yrlex)
 
 			for _, tag := range yrDollar[1].ss {
 				if tag == yrDollar[2].s {
-					return lexer.SetError(
+					return lexer.setError(
 						gyperror.DuplicateTagError, `duplicate tag "%s"`, yrDollar[2].s)
 				}
 			}
@@ -923,19 +1010,19 @@ yrdefault:
 		}
 	case 23:
 		yrDollar = yrS[yrpt-1 : yrpt+1]
-//line grammar.y:344
+//line parser/grammar.y:434
 		{
 			yrVAL.metas = []*ast.Meta{yrDollar[1].meta}
 		}
 	case 24:
 		yrDollar = yrS[yrpt-2 : yrpt+1]
-//line grammar.y:348
+//line parser/grammar.y:438
 		{
 			yrVAL.metas = append(yrDollar[1].metas, yrDollar[2].meta)
 		}
 	case 25:
 		yrDollar = yrS[yrpt-3 : yrpt+1]
-//line grammar.y:356
+//line parser/grammar.y:446
 		{
 			yrVAL.meta = &ast.Meta{
 				Key:   yrDollar[1].s,
@@ -944,7 +1031,7 @@ yrdefault:
 		}
 	case 26:
 		yrDollar = yrS[yrpt-3 : yrpt+1]
-//line grammar.y:363
+//line parser/grammar.y:453
 		{
 			yrVAL.meta = &ast.Meta{
 				Key:   yrDollar[1].s,
@@ -953,7 +1040,7 @@ yrdefault:
 		}
 	case 27:
 		yrDollar = yrS[yrpt-4 : yrpt+1]
-//line grammar.y:370
+//line parser/grammar.y:460
 		{
 			yrVAL.meta = &ast.Meta{
 				Key:   yrDollar[1].s,
@@ -962,7 +1049,7 @@ yrdefault:
 		}
 	case 28:
 		yrDollar = yrS[yrpt-3 : yrpt+1]
-//line grammar.y:377
+//line parser/grammar.y:467
 		{
 			yrVAL.meta = &ast.Meta{
 				Key:   yrDollar[1].s,
@@ -971,7 +1058,7 @@ yrdefault:
 		}
 	case 29:
 		yrDollar = yrS[yrpt-3 : yrpt+1]
-//line grammar.y:384
+//line parser/grammar.y:474
 		{
 			yrVAL.meta = &ast.Meta{
 				Key:   yrDollar[1].s,
@@ -980,19 +1067,19 @@ yrdefault:
 		}
 	case 30:
 		yrDollar = yrS[yrpt-1 : yrpt+1]
-//line grammar.y:395
+//line parser/grammar.y:485
 		{
 			yrVAL.yss = []ast.String{yrDollar[1].ys}
 		}
 	case 31:
 		yrDollar = yrS[yrpt-2 : yrpt+1]
-//line grammar.y:399
+//line parser/grammar.y:489
 		{
 			yrVAL.yss = append(yrDollar[1].yss, yrDollar[2].ys)
 		}
 	case 32:
 		yrDollar = yrS[yrpt-4 : yrpt+1]
-//line grammar.y:407
+//line parser/grammar.y:497
 		{
 			yrVAL.ys = &ast.TextString{
 				Identifier: strings.TrimPrefix(yrDollar[1].s, "$"),
@@ -1009,7 +1096,7 @@ yrdefault:
 		}
 	case 33:
 		yrDollar = yrS[yrpt-4 : yrpt+1]
-//line grammar.y:422
+//line parser/grammar.y:512
 		{
 			yrVAL.ys = &ast.RegexpString{
 				Identifier: strings.TrimPrefix(yrDollar[1].s, "$"),
@@ -1023,7 +1110,7 @@ yrdefault:
 		}
 	case 34:
 		yrDollar = yrS[yrpt-4 : yrpt+1]
-//line grammar.y:434
+//line parser/grammar.y:524
 		{
 			yrVAL.ys = &ast.HexString{
 				Identifier: strings.TrimPrefix(yrDollar[1].s, "$"),
@@ -1033,16 +1120,16 @@ yrdefault:
 		}
 	case 35:
 		yrDollar = yrS[yrpt-0 : yrpt+1]
-//line grammar.y:446
+//line parser/grammar.y:536
 		{
 			yrVAL.smod = stringModifiers{}
 		}
 	case 36:
 		yrDollar = yrS[yrpt-2 : yrpt+1]
-//line grammar.y:450
+//line parser/grammar.y:540
 		{
 			if yrDollar[1].smod.modifiers&yrDollar[2].smod.modifiers != 0 {
-				return asLexer(yrlex).SetError(
+				return asLexer(yrlex).setError(
 					gyperror.DuplicateModifierError, `duplicate modifier`)
 			}
 
@@ -1057,37 +1144,37 @@ yrdefault:
 		}
 	case 37:
 		yrDollar = yrS[yrpt-1 : yrpt+1]
-//line grammar.y:469
+//line parser/grammar.y:559
 		{
 			yrVAL.smod = stringModifiers{modifiers: ModWide}
 		}
 	case 38:
 		yrDollar = yrS[yrpt-1 : yrpt+1]
-//line grammar.y:470
+//line parser/grammar.y:560
 		{
 			yrVAL.smod = stringModifiers{modifiers: ModASCII}
 		}
 	case 39:
 		yrDollar = yrS[yrpt-1 : yrpt+1]
-//line grammar.y:471
+//line parser/grammar.y:561
 		{
 			yrVAL.smod = stringModifiers{modifiers: ModNocase}
 		}
 	case 40:
 		yrDollar = yrS[yrpt-1 : yrpt+1]
-//line grammar.y:472
+//line parser/grammar.y:562
 		{
 			yrVAL.smod = stringModifiers{modifiers: ModFullword}
 		}
 	case 41:
 		yrDollar = yrS[yrpt-1 : yrpt+1]
-//line grammar.y:473
+//line parser/grammar.y:563
 		{
 			yrVAL.smod = stringModifiers{modifiers: ModPrivate}
 		}
 	case 42:
 		yrDollar = yrS[yrpt-1 : yrpt+1]
-//line grammar.y:475
+//line parser/grammar.y:565
 		{
 			yrVAL.smod = stringModifiers{
 				modifiers: ModXor,
@@ -1097,7 +1184,7 @@ yrdefault:
 		}
 	case 43:
 		yrDollar = yrS[yrpt-4 : yrpt+1]
-//line grammar.y:483
+//line parser/grammar.y:573
 		{
 			yrVAL.smod = stringModifiers{
 				modifiers: ModXor,
@@ -1107,24 +1194,24 @@ yrdefault:
 		}
 	case 44:
 		yrDollar = yrS[yrpt-6 : yrpt+1]
-//line grammar.y:491
+//line parser/grammar.y:581
 		{
 			lexer := asLexer(yrlex)
 
 			if yrDollar[3].i64 < 0 {
-				return lexer.SetError(
+				return lexer.setError(
 					gyperror.InvalidStringModifierError,
 					"lower bound for xor range exceeded (min: 0)")
 			}
 
 			if yrDollar[5].i64 > 255 {
-				return lexer.SetError(
+				return lexer.setError(
 					gyperror.InvalidStringModifierError,
 					"upper bound for xor range exceeded (max: 255)")
 			}
 
 			if yrDollar[3].i64 > yrDollar[5].i64 {
-				return lexer.SetError(
+				return lexer.setError(
 					gyperror.InvalidStringModifierError,
 					"xor lower bound exceeds upper bound")
 			}
@@ -1137,73 +1224,73 @@ yrdefault:
 		}
 	case 45:
 		yrDollar = yrS[yrpt-0 : yrpt+1]
-//line grammar.y:523
+//line parser/grammar.y:613
 		{
 			yrVAL.mod = 0
 		}
 	case 46:
 		yrDollar = yrS[yrpt-2 : yrpt+1]
-//line grammar.y:527
+//line parser/grammar.y:617
 		{
 			yrVAL.mod = yrDollar[1].mod | yrDollar[2].mod
 		}
 	case 47:
 		yrDollar = yrS[yrpt-1 : yrpt+1]
-//line grammar.y:534
+//line parser/grammar.y:624
 		{
 			yrVAL.mod = ModWide
 		}
 	case 48:
 		yrDollar = yrS[yrpt-1 : yrpt+1]
-//line grammar.y:535
+//line parser/grammar.y:625
 		{
 			yrVAL.mod = ModASCII
 		}
 	case 49:
 		yrDollar = yrS[yrpt-1 : yrpt+1]
-//line grammar.y:536
+//line parser/grammar.y:626
 		{
 			yrVAL.mod = ModNocase
 		}
 	case 50:
 		yrDollar = yrS[yrpt-1 : yrpt+1]
-//line grammar.y:537
+//line parser/grammar.y:627
 		{
 			yrVAL.mod = ModFullword
 		}
 	case 51:
 		yrDollar = yrS[yrpt-1 : yrpt+1]
-//line grammar.y:538
+//line parser/grammar.y:628
 		{
 			yrVAL.mod = ModPrivate
 		}
 	case 52:
 		yrDollar = yrS[yrpt-0 : yrpt+1]
-//line grammar.y:544
+//line parser/grammar.y:634
 		{
 			yrVAL.mod = 0
 		}
 	case 53:
 		yrDollar = yrS[yrpt-2 : yrpt+1]
-//line grammar.y:548
+//line parser/grammar.y:638
 		{
 			yrVAL.mod = yrDollar[1].mod | yrDollar[2].mod
 		}
 	case 54:
 		yrDollar = yrS[yrpt-1 : yrpt+1]
-//line grammar.y:555
+//line parser/grammar.y:645
 		{
 			yrVAL.mod = ModPrivate
 		}
 	case 55:
 		yrDollar = yrS[yrpt-1 : yrpt+1]
-//line grammar.y:561
+//line parser/grammar.y:651
 		{
 			yrVAL.expr = &ast.Identifier{Identifier: yrDollar[1].s}
 		}
 	case 56:
 		yrDollar = yrS[yrpt-3 : yrpt+1]
-//line grammar.y:565
+//line parser/grammar.y:655
 		{
 			yrVAL.expr = &ast.MemberAccess{
 				Container: yrDollar[1].expr,
@@ -1212,7 +1299,7 @@ yrdefault:
 		}
 	case 57:
 		yrDollar = yrS[yrpt-4 : yrpt+1]
-//line grammar.y:572
+//line parser/grammar.y:662
 		{
 			yrVAL.expr = &ast.Subscripting{
 				Array: yrDollar[1].expr,
@@ -1221,7 +1308,7 @@ yrdefault:
 		}
 	case 58:
 		yrDollar = yrS[yrpt-4 : yrpt+1]
-//line grammar.y:579
+//line parser/grammar.y:669
 		{
 			yrVAL.expr = &ast.FunctionCall{
 				Callable:  yrDollar[1].expr,
@@ -1230,55 +1317,55 @@ yrdefault:
 		}
 	case 59:
 		yrDollar = yrS[yrpt-0 : yrpt+1]
-//line grammar.y:590
+//line parser/grammar.y:680
 		{
 			yrVAL.exprs = []ast.Expression{}
 		}
 	case 60:
 		yrDollar = yrS[yrpt-1 : yrpt+1]
-//line grammar.y:594
+//line parser/grammar.y:684
 		{
 			yrVAL.exprs = yrDollar[1].exprs
 		}
 	case 61:
 		yrDollar = yrS[yrpt-1 : yrpt+1]
-//line grammar.y:601
+//line parser/grammar.y:691
 		{
 			yrVAL.exprs = []ast.Expression{yrDollar[1].expr}
 		}
 	case 62:
 		yrDollar = yrS[yrpt-3 : yrpt+1]
-//line grammar.y:605
+//line parser/grammar.y:695
 		{
 			yrVAL.exprs = append(yrDollar[1].exprs, yrDollar[3].expr)
 		}
 	case 63:
 		yrDollar = yrS[yrpt-1 : yrpt+1]
-//line grammar.y:613
+//line parser/grammar.y:703
 		{
 			yrVAL.reg = yrDollar[1].reg
 		}
 	case 64:
 		yrDollar = yrS[yrpt-1 : yrpt+1]
-//line grammar.y:621
+//line parser/grammar.y:711
 		{
 			yrVAL.expr = yrDollar[1].expr
 		}
 	case 65:
 		yrDollar = yrS[yrpt-1 : yrpt+1]
-//line grammar.y:629
+//line parser/grammar.y:719
 		{
 			yrVAL.expr = ast.KeywordTrue
 		}
 	case 66:
 		yrDollar = yrS[yrpt-1 : yrpt+1]
-//line grammar.y:633
+//line parser/grammar.y:723
 		{
 			yrVAL.expr = ast.KeywordFalse
 		}
 	case 67:
 		yrDollar = yrS[yrpt-3 : yrpt+1]
-//line grammar.y:637
+//line parser/grammar.y:727
 		{
 			yrVAL.expr = &ast.Operation{
 				Operator: ast.OpMatches,
@@ -1287,7 +1374,7 @@ yrdefault:
 		}
 	case 68:
 		yrDollar = yrS[yrpt-3 : yrpt+1]
-//line grammar.y:644
+//line parser/grammar.y:734
 		{
 			yrVAL.expr = &ast.Operation{
 				Operator: ast.OpContains,
@@ -1296,7 +1383,7 @@ yrdefault:
 		}
 	case 69:
 		yrDollar = yrS[yrpt-1 : yrpt+1]
-//line grammar.y:651
+//line parser/grammar.y:741
 		{
 			yrVAL.expr = &ast.StringIdentifier{
 				Identifier: strings.TrimPrefix(yrDollar[1].s, "$"),
@@ -1304,7 +1391,7 @@ yrdefault:
 		}
 	case 70:
 		yrDollar = yrS[yrpt-3 : yrpt+1]
-//line grammar.y:657
+//line parser/grammar.y:747
 		{
 			yrVAL.expr = &ast.StringIdentifier{
 				Identifier: strings.TrimPrefix(yrDollar[1].s, "$"),
@@ -1313,7 +1400,7 @@ yrdefault:
 		}
 	case 71:
 		yrDollar = yrS[yrpt-3 : yrpt+1]
-//line grammar.y:664
+//line parser/grammar.y:754
 		{
 			yrVAL.expr = &ast.StringIdentifier{
 				Identifier: strings.TrimPrefix(yrDollar[1].s, "$"),
@@ -1322,12 +1409,12 @@ yrdefault:
 		}
 	case 72:
 		yrDollar = yrS[yrpt-3 : yrpt+1]
-//line grammar.y:670
+//line parser/grammar.y:760
 		{
 		}
 	case 73:
 		yrDollar = yrS[yrpt-9 : yrpt+1]
-//line grammar.y:672
+//line parser/grammar.y:762
 		{
 			yrVAL.expr = &ast.ForIn{
 				Quantifier: yrDollar[2].quantifier,
@@ -1338,7 +1425,7 @@ yrdefault:
 		}
 	case 74:
 		yrDollar = yrS[yrpt-8 : yrpt+1]
-//line grammar.y:681
+//line parser/grammar.y:771
 		{
 			yrVAL.expr = &ast.ForOf{
 				Quantifier: yrDollar[2].quantifier,
@@ -1348,7 +1435,7 @@ yrdefault:
 		}
 	case 75:
 		yrDollar = yrS[yrpt-3 : yrpt+1]
-//line grammar.y:689
+//line parser/grammar.y:779
 		{
 			yrVAL.expr = &ast.Of{
 				Quantifier: yrDollar[1].quantifier,
@@ -1357,25 +1444,25 @@ yrdefault:
 		}
 	case 76:
 		yrDollar = yrS[yrpt-2 : yrpt+1]
-//line grammar.y:696
+//line parser/grammar.y:786
 		{
 			yrVAL.expr = &ast.Not{yrDollar[2].expr}
 		}
 	case 77:
 		yrDollar = yrS[yrpt-3 : yrpt+1]
-//line grammar.y:700
+//line parser/grammar.y:790
 		{
 			yrVAL.expr = operation(ast.OpAnd, yrDollar[1].expr, yrDollar[3].expr)
 		}
 	case 78:
 		yrDollar = yrS[yrpt-3 : yrpt+1]
-//line grammar.y:704
+//line parser/grammar.y:794
 		{
 			yrVAL.expr = operation(ast.OpOr, yrDollar[1].expr, yrDollar[3].expr)
 		}
 	case 79:
 		yrDollar = yrS[yrpt-3 : yrpt+1]
-//line grammar.y:708
+//line parser/grammar.y:798
 		{
 			yrVAL.expr = &ast.Operation{
 				Operator: ast.OpLessThan,
@@ -1384,7 +1471,7 @@ yrdefault:
 		}
 	case 80:
 		yrDollar = yrS[yrpt-3 : yrpt+1]
-//line grammar.y:715
+//line parser/grammar.y:805
 		{
 			yrVAL.expr = &ast.Operation{
 				Operator: ast.OpGreaterThan,
@@ -1393,7 +1480,7 @@ yrdefault:
 		}
 	case 81:
 		yrDollar = yrS[yrpt-3 : yrpt+1]
-//line grammar.y:722
+//line parser/grammar.y:812
 		{
 			yrVAL.expr = &ast.Operation{
 				Operator: ast.OpLessOrEqual,
@@ -1402,7 +1489,7 @@ yrdefault:
 		}
 	case 82:
 		yrDollar = yrS[yrpt-3 : yrpt+1]
-//line grammar.y:729
+//line parser/grammar.y:819
 		{
 			yrVAL.expr = &ast.Operation{
 				Operator: ast.OpGreaterOrEqual,
@@ -1411,7 +1498,7 @@ yrdefault:
 		}
 	case 83:
 		yrDollar = yrS[yrpt-3 : yrpt+1]
-//line grammar.y:736
+//line parser/grammar.y:826
 		{
 			yrVAL.expr = &ast.Operation{
 				Operator: ast.OpEqual,
@@ -1420,7 +1507,7 @@ yrdefault:
 		}
 	case 84:
 		yrDollar = yrS[yrpt-3 : yrpt+1]
-//line grammar.y:743
+//line parser/grammar.y:833
 		{
 			yrVAL.expr = &ast.Operation{
 				Operator: ast.OpNotEqual,
@@ -1429,31 +1516,31 @@ yrdefault:
 		}
 	case 85:
 		yrDollar = yrS[yrpt-1 : yrpt+1]
-//line grammar.y:750
+//line parser/grammar.y:840
 		{
 			yrVAL.expr = yrDollar[1].expr
 		}
 	case 86:
 		yrDollar = yrS[yrpt-3 : yrpt+1]
-//line grammar.y:754
+//line parser/grammar.y:844
 		{
 			yrVAL.expr = &ast.Group{yrDollar[2].expr}
 		}
 	case 87:
 		yrDollar = yrS[yrpt-3 : yrpt+1]
-//line grammar.y:762
+//line parser/grammar.y:852
 		{
 			yrVAL.node = &ast.Enum{Values: yrDollar[2].exprs}
 		}
 	case 88:
 		yrDollar = yrS[yrpt-1 : yrpt+1]
-//line grammar.y:766
+//line parser/grammar.y:856
 		{
 			yrVAL.node = yrDollar[1].rng
 		}
 	case 89:
 		yrDollar = yrS[yrpt-5 : yrpt+1]
-//line grammar.y:774
+//line parser/grammar.y:864
 		{
 			yrVAL.rng = &ast.Range{
 				Start: yrDollar[2].expr,
@@ -1462,43 +1549,43 @@ yrdefault:
 		}
 	case 90:
 		yrDollar = yrS[yrpt-1 : yrpt+1]
-//line grammar.y:785
+//line parser/grammar.y:875
 		{
 			yrVAL.exprs = []ast.Expression{yrDollar[1].expr}
 		}
 	case 91:
 		yrDollar = yrS[yrpt-3 : yrpt+1]
-//line grammar.y:789
+//line parser/grammar.y:879
 		{
 			yrVAL.exprs = append(yrDollar[1].exprs, yrDollar[3].expr)
 		}
 	case 92:
 		yrDollar = yrS[yrpt-3 : yrpt+1]
-//line grammar.y:797
+//line parser/grammar.y:887
 		{
 			yrVAL.node = &ast.Enum{Values: yrDollar[2].exprs}
 		}
 	case 93:
 		yrDollar = yrS[yrpt-1 : yrpt+1]
-//line grammar.y:801
+//line parser/grammar.y:891
 		{
 			yrVAL.node = ast.KeywordThem
 		}
 	case 94:
 		yrDollar = yrS[yrpt-1 : yrpt+1]
-//line grammar.y:809
+//line parser/grammar.y:899
 		{
 			yrVAL.exprs = []ast.Expression{yrDollar[1].si}
 		}
 	case 95:
 		yrDollar = yrS[yrpt-3 : yrpt+1]
-//line grammar.y:813
+//line parser/grammar.y:903
 		{
 			yrVAL.exprs = append(yrDollar[1].exprs, yrDollar[3].si)
 		}
 	case 96:
 		yrDollar = yrS[yrpt-1 : yrpt+1]
-//line grammar.y:821
+//line parser/grammar.y:911
 		{
 			yrVAL.si = &ast.StringIdentifier{
 				Identifier: strings.TrimPrefix(yrDollar[1].s, "$"),
@@ -1506,7 +1593,7 @@ yrdefault:
 		}
 	case 97:
 		yrDollar = yrS[yrpt-1 : yrpt+1]
-//line grammar.y:827
+//line parser/grammar.y:917
 		{
 			yrVAL.si = &ast.StringIdentifier{
 				Identifier: strings.TrimPrefix(yrDollar[1].s, "$"),
@@ -1514,67 +1601,67 @@ yrdefault:
 		}
 	case 98:
 		yrDollar = yrS[yrpt-1 : yrpt+1]
-//line grammar.y:837
+//line parser/grammar.y:927
 		{
 			yrVAL.quantifier = &ast.Quantifier{yrDollar[1].expr}
 		}
 	case 99:
 		yrDollar = yrS[yrpt-1 : yrpt+1]
-//line grammar.y:841
+//line parser/grammar.y:931
 		{
 			yrVAL.quantifier = &ast.Quantifier{ast.KeywordAll}
 		}
 	case 100:
 		yrDollar = yrS[yrpt-1 : yrpt+1]
-//line grammar.y:845
+//line parser/grammar.y:935
 		{
 			yrVAL.quantifier = &ast.Quantifier{ast.KeywordAny}
 		}
 	case 101:
 		yrDollar = yrS[yrpt-1 : yrpt+1]
-//line grammar.y:853
+//line parser/grammar.y:943
 		{
 			yrVAL.ss = []string{yrDollar[1].s}
 		}
 	case 102:
 		yrDollar = yrS[yrpt-3 : yrpt+1]
-//line grammar.y:857
+//line parser/grammar.y:947
 		{
 			yrVAL.ss = append(yrDollar[1].ss, yrDollar[3].s)
 		}
 	case 103:
 		yrDollar = yrS[yrpt-1 : yrpt+1]
-//line grammar.y:864
+//line parser/grammar.y:954
 		{
 			yrVAL.node = yrDollar[1].expr
 		}
 	case 104:
 		yrDollar = yrS[yrpt-1 : yrpt+1]
-//line grammar.y:868
+//line parser/grammar.y:958
 		{
 			yrVAL.node = yrDollar[1].node
 		}
 	case 105:
 		yrDollar = yrS[yrpt-3 : yrpt+1]
-//line grammar.y:876
+//line parser/grammar.y:966
 		{
 			yrVAL.expr = &ast.Group{yrDollar[2].expr}
 		}
 	case 106:
 		yrDollar = yrS[yrpt-1 : yrpt+1]
-//line grammar.y:880
+//line parser/grammar.y:970
 		{
 			yrVAL.expr = ast.KeywordFilesize
 		}
 	case 107:
 		yrDollar = yrS[yrpt-1 : yrpt+1]
-//line grammar.y:884
+//line parser/grammar.y:974
 		{
 			yrVAL.expr = ast.KeywordEntrypoint
 		}
 	case 108:
 		yrDollar = yrS[yrpt-4 : yrpt+1]
-//line grammar.y:888
+//line parser/grammar.y:978
 		{
 			yrVAL.expr = &ast.FunctionCall{
 				Callable:  &ast.Identifier{Identifier: yrDollar[1].s},
@@ -1583,25 +1670,25 @@ yrdefault:
 		}
 	case 109:
 		yrDollar = yrS[yrpt-1 : yrpt+1]
-//line grammar.y:895
+//line parser/grammar.y:985
 		{
 			yrVAL.expr = &ast.LiteralInteger{yrDollar[1].i64}
 		}
 	case 110:
 		yrDollar = yrS[yrpt-1 : yrpt+1]
-//line grammar.y:899
+//line parser/grammar.y:989
 		{
 			yrVAL.expr = &ast.LiteralFloat{yrDollar[1].f64}
 		}
 	case 111:
 		yrDollar = yrS[yrpt-1 : yrpt+1]
-//line grammar.y:903
+//line parser/grammar.y:993
 		{
 			yrVAL.expr = &ast.LiteralString{yrDollar[1].s}
 		}
 	case 112:
 		yrDollar = yrS[yrpt-1 : yrpt+1]
-//line grammar.y:907
+//line parser/grammar.y:997
 		{
 			yrVAL.expr = &ast.StringCount{
 				Identifier: strings.TrimPrefix(yrDollar[1].s, "#"),
@@ -1609,7 +1696,7 @@ yrdefault:
 		}
 	case 113:
 		yrDollar = yrS[yrpt-4 : yrpt+1]
-//line grammar.y:913
+//line parser/grammar.y:1003
 		{
 			yrVAL.expr = &ast.StringOffset{
 				Identifier: strings.TrimPrefix(yrDollar[1].s, "@"),
@@ -1618,7 +1705,7 @@ yrdefault:
 		}
 	case 114:
 		yrDollar = yrS[yrpt-1 : yrpt+1]
-//line grammar.y:920
+//line parser/grammar.y:1010
 		{
 			yrVAL.expr = &ast.StringOffset{
 				Identifier: strings.TrimPrefix(yrDollar[1].s, "@"),
@@ -1626,7 +1713,7 @@ yrdefault:
 		}
 	case 115:
 		yrDollar = yrS[yrpt-4 : yrpt+1]
-//line grammar.y:926
+//line parser/grammar.y:1016
 		{
 			yrVAL.expr = &ast.StringLength{
 				Identifier: strings.TrimPrefix(yrDollar[1].s, "!"),
@@ -1635,7 +1722,7 @@ yrdefault:
 		}
 	case 116:
 		yrDollar = yrS[yrpt-1 : yrpt+1]
-//line grammar.y:933
+//line parser/grammar.y:1023
 		{
 			yrVAL.expr = &ast.StringLength{
 				Identifier: strings.TrimPrefix(yrDollar[1].s, "!"),
@@ -1643,85 +1730,85 @@ yrdefault:
 		}
 	case 117:
 		yrDollar = yrS[yrpt-1 : yrpt+1]
-//line grammar.y:939
+//line parser/grammar.y:1029
 		{
 			yrVAL.expr = yrDollar[1].expr
 		}
 	case 118:
 		yrDollar = yrS[yrpt-2 : yrpt+1]
-//line grammar.y:943
+//line parser/grammar.y:1033
 		{
 			yrVAL.expr = &ast.Minus{yrDollar[2].expr}
 		}
 	case 119:
 		yrDollar = yrS[yrpt-3 : yrpt+1]
-//line grammar.y:947
+//line parser/grammar.y:1037
 		{
 			yrVAL.expr = operation(ast.OpAdd, yrDollar[1].expr, yrDollar[3].expr)
 		}
 	case 120:
 		yrDollar = yrS[yrpt-3 : yrpt+1]
-//line grammar.y:951
+//line parser/grammar.y:1041
 		{
 			yrVAL.expr = operation(ast.OpSub, yrDollar[1].expr, yrDollar[3].expr)
 		}
 	case 121:
 		yrDollar = yrS[yrpt-3 : yrpt+1]
-//line grammar.y:955
+//line parser/grammar.y:1045
 		{
 			yrVAL.expr = operation(ast.OpMul, yrDollar[1].expr, yrDollar[3].expr)
 		}
 	case 122:
 		yrDollar = yrS[yrpt-3 : yrpt+1]
-//line grammar.y:959
+//line parser/grammar.y:1049
 		{
 			yrVAL.expr = operation(ast.OpDiv, yrDollar[1].expr, yrDollar[3].expr)
 		}
 	case 123:
 		yrDollar = yrS[yrpt-3 : yrpt+1]
-//line grammar.y:963
+//line parser/grammar.y:1053
 		{
 			yrVAL.expr = operation(ast.OpMod, yrDollar[1].expr, yrDollar[3].expr)
 		}
 	case 124:
 		yrDollar = yrS[yrpt-3 : yrpt+1]
-//line grammar.y:967
+//line parser/grammar.y:1057
 		{
 			yrVAL.expr = operation(ast.OpBitXor, yrDollar[1].expr, yrDollar[3].expr)
 		}
 	case 125:
 		yrDollar = yrS[yrpt-3 : yrpt+1]
-//line grammar.y:971
+//line parser/grammar.y:1061
 		{
 			yrVAL.expr = operation(ast.OpBitAnd, yrDollar[1].expr, yrDollar[3].expr)
 		}
 	case 126:
 		yrDollar = yrS[yrpt-3 : yrpt+1]
-//line grammar.y:975
+//line parser/grammar.y:1065
 		{
 			yrVAL.expr = operation(ast.OpBitOr, yrDollar[1].expr, yrDollar[3].expr)
 		}
 	case 127:
 		yrDollar = yrS[yrpt-2 : yrpt+1]
-//line grammar.y:979
+//line parser/grammar.y:1069
 		{
 			yrVAL.expr = &ast.BitwiseNot{yrDollar[2].expr}
 		}
 	case 128:
 		yrDollar = yrS[yrpt-3 : yrpt+1]
-//line grammar.y:983
+//line parser/grammar.y:1073
 		{
 			yrVAL.expr = operation(ast.OpShiftLeft, yrDollar[1].expr, yrDollar[3].expr)
 		}
 	case 129:
 		yrDollar = yrS[yrpt-3 : yrpt+1]
-//line grammar.y:987
+//line parser/grammar.y:1077
 		{
 			yrVAL.expr = operation(ast.OpShiftRight, yrDollar[1].expr, yrDollar[3].expr)
 		}
 	case 130:
 		yrDollar = yrS[yrpt-1 : yrpt+1]
-//line grammar.y:991
+//line parser/grammar.y:1081
 		{
 			yrVAL.expr = yrDollar[1].reg
 		}