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/*
8Package syntax parses regular expressions into parse trees and compiles
9parse trees into programs. Most clients of regular expressions will use the
10facilities of package [regexp] (such as [regexp.Compile] and [regexp.Match]) instead of this package.
11
12# Syntax
13
14The regular expression syntax understood by this package when parsing with the [Perl] flag is as follows.
15Parts of the syntax can be disabled by passing alternate flags to [Parse].
16
17Single 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
31Composites:
32
33	xy             x followed by y
34	x|y            x or y (prefer x)
35
36Repetitions:
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
51Implementation restriction: The counting forms x{n,m}, x{n,}, and x{n}
52reject forms that create a minimum or maximum repetition count above 1000.
53Unlimited repetitions are not subject to this restriction.
54
55Grouping:
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
71Empty 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
80Escape 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
94Character 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
103Named 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
114Perl 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
123ASCII 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
140Unicode character classes are those in [unicode.Categories] and [unicode.Scripts].
141*/
142package syntax
143