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Source file src/regexp/syntax/doc.go

     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	// DO NOT EDIT. This file is generated by mksyntaxgo from the RE2 distribution.
     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 Compile and 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	
    18	Single characters:
    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	  xy             x followed by y
    33	  x|y            x or y (prefer x)
    34	
    35	Repetitions:
    36	  x*             zero or more x, prefer more
    37	  x+             one or more x, prefer more
    38	  x?             zero or one x, prefer one
    39	  x{n,m}         n or n+1 or ... or m x, prefer more
    40	  x{n,}          n or more x, prefer more
    41	  x{n}           exactly n x
    42	  x*?            zero or more x, prefer fewer
    43	  x+?            one or more x, prefer fewer
    44	  x??            zero or one x, prefer zero
    45	  x{n,m}?        n or n+1 or ... or m x, prefer fewer
    46	  x{n,}?         n or more x, prefer fewer
    47	  x{n}?          exactly n x
    48	
    49	Implementation restriction: The counting forms x{n,m}, x{n,}, and x{n}
    50	reject forms that create a minimum or maximum repetition count above 1000.
    51	Unlimited repetitions are not subject to this restriction.
    52	
    53	Grouping:
    54	  (re)           numbered capturing group (submatch)
    55	  (?P<name>re)   named & numbered capturing group (submatch)
    56	  (?:re)         non-capturing group
    57	  (?flags)       set flags within current group; non-capturing
    58	  (?flags:re)    set flags during re; non-capturing
    59	
    60	  Flag syntax is xyz (set) or -xyz (clear) or xy-z (set xy, clear z). The flags are:
    61	
    62	  i              case-insensitive (default false)
    63	  m              multi-line mode: ^ and $ match begin/end line in addition to begin/end text (default false)
    64	  s              let . match \n (default false)
    65	  U              ungreedy: swap meaning of x* and x*?, x+ and x+?, etc (default false)
    66	
    67	Empty strings:
    68	  ^              at beginning of text or line (flag m=true)
    69	  $              at end of text (like \z not Perl's \Z) or line (flag m=true)
    70	  \A             at beginning of text
    71	  \b             at ASCII word boundary (\w on one side and \W, \A, or \z on the other)
    72	  \B             not at ASCII word boundary
    73	  \z             at end of text
    74	
    75	Escape sequences:
    76	  \a             bell (== \007)
    77	  \f             form feed (== \014)
    78	  \t             horizontal tab (== \011)
    79	  \n             newline (== \012)
    80	  \r             carriage return (== \015)
    81	  \v             vertical tab character (== \013)
    82	  \*             literal *, for any punctuation character *
    83	  \123           octal character code (up to three digits)
    84	  \x7F           hex character code (exactly two digits)
    85	  \x{10FFFF}     hex character code
    86	  \Q...\E        literal text ... even if ... has punctuation
    87	
    88	Character class elements:
    89	  x              single character
    90	  A-Z            character range (inclusive)
    91	  \d             Perl character class
    92	  [:foo:]        ASCII character class foo
    93	  \p{Foo}        Unicode character class Foo
    94	  \pF            Unicode character class F (one-letter name)
    95	
    96	Named character classes as character class elements:
    97	  [\d]           digits (== \d)
    98	  [^\d]          not digits (== \D)
    99	  [\D]           not digits (== \D)
   100	  [^\D]          not not digits (== \d)
   101	  [[:name:]]     named ASCII class inside character class (== [:name:])
   102	  [^[:name:]]    named ASCII class inside negated character class (== [:^name:])
   103	  [\p{Name}]     named Unicode property inside character class (== \p{Name})
   104	  [^\p{Name}]    named Unicode property inside negated character class (== \P{Name})
   105	
   106	Perl character classes (all ASCII-only):
   107	  \d             digits (== [0-9])
   108	  \D             not digits (== [^0-9])
   109	  \s             whitespace (== [\t\n\f\r ])
   110	  \S             not whitespace (== [^\t\n\f\r ])
   111	  \w             word characters (== [0-9A-Za-z_])
   112	  \W             not word characters (== [^0-9A-Za-z_])
   113	
   114	ASCII character classes:
   115	  [[:alnum:]]    alphanumeric (== [0-9A-Za-z])
   116	  [[:alpha:]]    alphabetic (== [A-Za-z])
   117	  [[:ascii:]]    ASCII (== [\x00-\x7F])
   118	  [[:blank:]]    blank (== [\t ])
   119	  [[:cntrl:]]    control (== [\x00-\x1F\x7F])
   120	  [[:digit:]]    digits (== [0-9])
   121	  [[:graph:]]    graphical (== [!-~] == [A-Za-z0-9!"#$%&'()*+,\-./:;<=>?@[\\\]^_`{|}~])
   122	  [[:lower:]]    lower case (== [a-z])
   123	  [[:print:]]    printable (== [ -~] == [ [:graph:]])
   124	  [[:punct:]]    punctuation (== [!-/:-@[-`{-~])
   125	  [[:space:]]    whitespace (== [\t\n\v\f\r ])
   126	  [[:upper:]]    upper case (== [A-Z])
   127	  [[:word:]]     word characters (== [0-9A-Za-z_])
   128	  [[:xdigit:]]   hex digit (== [0-9A-Fa-f])
   129	
   130	*/
   131	package syntax
   132	

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