1 // Copyright 2012 The Go Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style 3 // license that can be found in the LICENSE file. 4 5 // Code generated by mksyntaxgo from the RE2 distribution. DO NOT EDIT. 6 7 /* 8 Package syntax parses regular expressions into parse trees and compiles 9 parse trees into programs. Most clients of regular expressions will use the 10 facilities of package [regexp] (such as [regexp.Compile] and [regexp.Match]) instead of this package. 11 12 # Syntax 13 14 The regular expression syntax understood by this package when parsing with the [Perl] flag is as follows. 15 Parts of the syntax can be disabled by passing alternate flags to [Parse]. 16 17 Single characters: 18 19 . any character, possibly including newline (flag s=true) 20 [xyz] character class 21 [^xyz] negated character class 22 \d Perl character class 23 \D negated Perl character class 24 [[:alpha:]] ASCII character class 25 [[:^alpha:]] negated ASCII character class 26 \pN Unicode character class (one-letter name) 27 \p{Greek} Unicode character class 28 \PN negated Unicode character class (one-letter name) 29 \P{Greek} negated Unicode character class 30 31 Composites: 32 33 xy x followed by y 34 x|y x or y (prefer x) 35 36 Repetitions: 37 38 x* zero or more x, prefer more 39 x+ one or more x, prefer more 40 x? zero or one x, prefer one 41 x{n,m} n or n+1 or ... or m x, prefer more 42 x{n,} n or more x, prefer more 43 x{n} exactly n x 44 x*? zero or more x, prefer fewer 45 x+? one or more x, prefer fewer 46 x?? zero or one x, prefer zero 47 x{n,m}? n or n+1 or ... or m x, prefer fewer 48 x{n,}? n or more x, prefer fewer 49 x{n}? exactly n x 50 51 Implementation restriction: The counting forms x{n,m}, x{n,}, and x{n} 52 reject forms that create a minimum or maximum repetition count above 1000. 53 Unlimited repetitions are not subject to this restriction. 54 55 Grouping: 56 57 (re) numbered capturing group (submatch) 58 (?P<name>re) named & numbered capturing group (submatch) 59 (?<name>re) named & numbered capturing group (submatch) 60 (?:re) non-capturing group 61 (?flags) set flags within current group; non-capturing 62 (?flags:re) set flags during re; non-capturing 63 64 Flag syntax is xyz (set) or -xyz (clear) or xy-z (set xy, clear z). The flags are: 65 66 i case-insensitive (default false) 67 m multi-line mode: ^ and $ match begin/end line in addition to begin/end text (default false) 68 s let . match \n (default false) 69 U ungreedy: swap meaning of x* and x*?, x+ and x+?, etc (default false) 70 71 Empty strings: 72 73 ^ at beginning of text or line (flag m=true) 74 $ at end of text (like \z not \Z) or line (flag m=true) 75 \A at beginning of text 76 \b at ASCII word boundary (\w on one side and \W, \A, or \z on the other) 77 \B not at ASCII word boundary 78 \z at end of text 79 80 Escape sequences: 81 82 \a bell (== \007) 83 \f form feed (== \014) 84 \t horizontal tab (== \011) 85 \n newline (== \012) 86 \r carriage return (== \015) 87 \v vertical tab character (== \013) 88 \* literal *, for any punctuation character * 89 \123 octal character code (up to three digits) 90 \x7F hex character code (exactly two digits) 91 \x{10FFFF} hex character code 92 \Q...\E literal text ... even if ... has punctuation 93 94 Character class elements: 95 96 x single character 97 A-Z character range (inclusive) 98 \d Perl character class 99 [:foo:] ASCII character class foo 100 \p{Foo} Unicode character class Foo 101 \pF Unicode character class F (one-letter name) 102 103 Named character classes as character class elements: 104 105 [\d] digits (== \d) 106 [^\d] not digits (== \D) 107 [\D] not digits (== \D) 108 [^\D] not not digits (== \d) 109 [[:name:]] named ASCII class inside character class (== [:name:]) 110 [^[:name:]] named ASCII class inside negated character class (== [:^name:]) 111 [\p{Name}] named Unicode property inside character class (== \p{Name}) 112 [^\p{Name}] named Unicode property inside negated character class (== \P{Name}) 113 114 Perl character classes (all ASCII-only): 115 116 \d digits (== [0-9]) 117 \D not digits (== [^0-9]) 118 \s whitespace (== [\t\n\f\r ]) 119 \S not whitespace (== [^\t\n\f\r ]) 120 \w word characters (== [0-9A-Za-z_]) 121 \W not word characters (== [^0-9A-Za-z_]) 122 123 ASCII character classes: 124 125 [[:alnum:]] alphanumeric (== [0-9A-Za-z]) 126 [[:alpha:]] alphabetic (== [A-Za-z]) 127 [[:ascii:]] ASCII (== [\x00-\x7F]) 128 [[:blank:]] blank (== [\t ]) 129 [[:cntrl:]] control (== [\x00-\x1F\x7F]) 130 [[:digit:]] digits (== [0-9]) 131 [[:graph:]] graphical (== [!-~] == [A-Za-z0-9!"#$%&'()*+,\-./:;<=>?@[\\\]^_`{|}~]) 132 [[:lower:]] lower case (== [a-z]) 133 [[:print:]] printable (== [ -~] == [ [:graph:]]) 134 [[:punct:]] punctuation (== [!-/:-@[-`{-~]) 135 [[:space:]] whitespace (== [\t\n\v\f\r ]) 136 [[:upper:]] upper case (== [A-Z]) 137 [[:word:]] word characters (== [0-9A-Za-z_]) 138 [[:xdigit:]] hex digit (== [0-9A-Fa-f]) 139 140 Unicode character classes are those in [unicode.Categories] and [unicode.Scripts]. 141 */ 142 package syntax 143