-/*!
-
- @page resyn_overview Syntax of the builtin regular expression library
-
- A @e regular expression describes strings of characters. It's a
- pattern that matches certain strings and doesn't match others.
- @b See also
- #wxRegEx
- @ref differentflavors_overview
- @ref resyntax_overview
- @ref resynbracket_overview
- #Escapes
- #Metasyntax
- #Matching
- @ref relimits_overview
- @ref resynbre_overview
- @ref resynchars_overview
-
-
- @section differentflavors Different Flavors of REs
-
- @ref resyn_overview
- Regular expressions ("RE''s), as defined by POSIX, come in two
- flavors: @e extended REs ("EREs'') and @e basic REs ("BREs''). EREs are roughly those
- of the traditional @e egrep, while BREs are roughly those of the traditional
- @e ed. This implementation adds a third flavor, @e advanced REs ("AREs''), basically
- EREs with some significant extensions.
- This manual page primarily describes
- AREs. BREs mostly exist for backward compatibility in some old programs;
- they will be discussed at the #end. POSIX EREs are almost an exact subset
- of AREs. Features of AREs that are not present in EREs will be indicated.
-
- @section resyntax Regular Expression Syntax
-
- @ref resyn_overview
- These regular expressions are implemented using
- the package written by Henry Spencer, based on the 1003.2 spec and some
- (not quite all) of the Perl5 extensions (thanks, Henry!). Much of the description
- of regular expressions below is copied verbatim from his manual entry.
- An ARE is one or more @e branches, separated by '@b |', matching anything that matches
- any of the branches.
- A branch is zero or more @e constraints or @e quantified
- atoms, concatenated. It matches a match for the first, followed by a match
- for the second, etc; an empty branch matches the empty string.
- A quantified atom is an @e atom possibly followed by a single @e quantifier. Without a quantifier,
- it matches a match for the atom. The quantifiers, and what a so-quantified
- atom matches, are:
-
-
-
-
-
-
- @b *
-
-
-
-
- a sequence of 0 or more matches of the atom
-
-
-
-
-
- @b +
-
-
-
-
- a sequence of 1 or more matches of the atom
-
-
-
-
-
- @b ?
-
-
-
-
- a sequence of 0 or 1 matches of the atom
-
-
-
-
-
- @b {m}
-
-
-
-
- a sequence of exactly @e m matches of the atom
-
-
-
-
-
- @b {m,}
-
-
-
-
- a sequence of @e m or more matches of the atom
-
-
-
-
-
- @b {m,n}
-
-
-
-
- a sequence of @e m through @e n (inclusive)
- matches of the atom; @e m may not exceed @e n
-
-
-
-
-
- @b *? +? ?? {m}? {m,}? {m,n}?
-
-
-
-
- @e non-greedy quantifiers,
- which match the same possibilities, but prefer the
- smallest number rather than the largest number of matches (see #Matching)
-
-
-
-
-
- The forms using @b { and @b } are known as @e bounds. The numbers @e m and @e n are unsigned
- decimal integers with permissible values from 0 to 255 inclusive.
- An atom is one of:
-
-
-
-
-
-
- @b (re)
-
-
-
-
- (where @e re is any regular expression) matches a match for
- @e re, with the match noted for possible reporting
-
-
-
-
-
- @b (?:re)
-
-
-
-
- as previous, but
- does no reporting (a "non-capturing'' set of parentheses)
-
-
-
-
-
- @b ()
-
-
-
-
- matches an empty
- string, noted for possible reporting
-
-
-
-
-
- @b (?:)
-
-
-
-
- matches an empty string, without reporting
-
-
-
-
-
- @b [chars]
-
-
-
-
- a @e bracket expression, matching any one of the @e chars
- (see @ref resynbracket_overview for more detail)
-
-
-
-
-
- @b .
-
-
-
-
- matches any single character
-
-
-
-
-
- @b \k
-
-
-
-
- (where @e k is a non-alphanumeric character)
- matches that character taken as an ordinary character, e.g. \\ matches a backslash
- character
-
-
-
-
-
- @b \c
-
-
-
-
- where @e c is alphanumeric (possibly followed by other characters),
- an @e escape (AREs only), see #Escapes below
-
-
-
-
-
- @b {
-
-
-
-
- when followed by a character
- other than a digit, matches the left-brace character '@b {'; when followed by
- a digit, it is the beginning of a @e bound (see above)
-
-
-
-
-
- @b x
-
-
-
-
- where @e x is a single
- character with no other significance, matches that character.
-
-
-
-
-
- A @e constraint matches an empty string when specific conditions are met. A constraint may
- not be followed by a quantifier. The simple constraints are as follows;
- some more constraints are described later, under #Escapes.
-
-
-
-
-
-
- @b ^
-
-
-
-
- matches at the beginning of a line
-
-
-
-
-
- @b $
-
-
-
-
- matches at the end of a line
-
-
-
-
-
- @b (?=re)
-
-
-
-
- @e positive lookahead
- (AREs only), matches at any point where a substring matching @e re begins
-
-
-
-
-
- @b (?!re)
-
-
-
-
- @e negative lookahead (AREs only),
- matches at any point where no substring matching @e re begins
-
-
-
-
-
- The lookahead constraints may not contain back references
- (see later), and all parentheses within them are considered non-capturing.
- An RE may not end with '@b \'.
-
- @section wxresynbracket Bracket Expressions
-
- @ref resyn_overview
- A @e bracket expression is a list
- of characters enclosed in '@b []'. It normally matches any single character from
- the list (but see below). If the list begins with '@b ^', it matches any single
- character (but see below) @e not from the rest of the list.
- If two characters
- in the list are separated by '@b -', this is shorthand for the full @e range of
- characters between those two (inclusive) in the collating sequence, e.g.
- @b [0-9] in ASCII matches any decimal digit. Two ranges may not share an endpoint,
- so e.g. @b a-c-e is illegal. Ranges are very collating-sequence-dependent, and portable
- programs should avoid relying on them.
- To include a literal @b ] or @b - in the
- list, the simplest method is to enclose it in @b [. and @b .] to make it a collating
- element (see below). Alternatively, make it the first character (following
- a possible '@b ^'), or (AREs only) precede it with '@b \'.
- Alternatively, for '@b -', make
- it the last character, or the second endpoint of a range. To use a literal
- @b - as the first endpoint of a range, make it a collating element or (AREs
- only) precede it with '@b \'. With the exception of these, some combinations using
- @b [ (see next paragraphs), and escapes, all other special characters lose
- their special significance within a bracket expression.
- Within a bracket
- expression, a collating element (a character, a multi-character sequence
- that collates as if it were a single character, or a collating-sequence
- name for either) enclosed in @b [. and @b .] stands for the
- sequence of characters of that collating element.
- @e wxWidgets: Currently no multi-character collating elements are defined.
- So in @b [.X.], @e X can either be a single character literal or
- the name of a character. For example, the following are both identical
- @b [[.0.]-[.9.]] and @b [[.zero.]-[.nine.]] and mean the same as
- @b [0-9].
- See @ref resynchars_overview.
- Within a bracket expression, a collating element enclosed in @b [= and @b =]
- is an equivalence class, standing for the sequences of characters of all
- collating elements equivalent to that one, including itself.
- An equivalence class may not be an endpoint of a range.
- @e wxWidgets: Currently no equivalence classes are defined, so
- @b [=X=] stands for just the single character @e X.
- @e X can either be a single character literal or the name of a character,
- see @ref resynchars_overview.
- Within a bracket expression,
- the name of a @e character class enclosed in @b [: and @b :] stands for the list
- of all characters (not all collating elements!) belonging to that class.
- Standard character classes are:
-
-
-
-
-
-
- @b alpha
-
-
-
-
- A letter.
-
-
-
-
-
- @b upper
-
-
-
-
- An upper-case letter.
-
-
-
-
-
- @b lower
-
-
-
-
- A lower-case letter.
-
-
-
-
-
- @b digit
-
-
-
-
- A decimal digit.
-
-
-
-
-
- @b xdigit
-
-
-
-
- A hexadecimal digit.
-
-
-
-
-
- @b alnum
-
-
-
-
- An alphanumeric (letter or digit).
-
-
-
-
-
- @b print
-
-
-
-
- An alphanumeric (same as alnum).
-
-
-
-
-
- @b blank
-
-
-
-
- A space or tab character.
-
-
-
-
-
- @b space
-
-
-
-
- A character producing white space in displayed text.
-
-
-
-
-
- @b punct
-
-
-
-
- A punctuation character.
-
-
-
-
-
- @b graph
-
-
-
-
- A character with a visible representation.
-
-
-
-
-
- @b cntrl
-
-
-
-
- A control character.
-
-
-
-
-
- A character class may not be used as an endpoint of a range.
- @e wxWidgets: In a non-Unicode build, these character classifications depend on the
- current locale, and correspond to the values return by the ANSI C 'is'
- functions: isalpha, isupper, etc. In Unicode mode they are based on
- Unicode classifications, and are not affected by the current locale.
- There are two special cases of bracket expressions:
- the bracket expressions @b [[::]] and @b [[::]] are constraints, matching empty
- strings at the beginning and end of a word respectively. A word is defined
- as a sequence of word characters that is neither preceded nor followed
- by word characters. A word character is an @e alnum character or an underscore
- (@b _). These special bracket expressions are deprecated; users of AREs should
- use constraint escapes instead (see #Escapes below).
-
- @section wxresynescapes Escapes
-
- @ref resyn_overview
- Escapes (AREs only),
- which begin with a @b \ followed by an alphanumeric character, come in several
- varieties: character entry, class shorthands, constraint escapes, and back
- references. A @b \ followed by an alphanumeric character but not constituting
- a valid escape is illegal in AREs. In EREs, there are no escapes: outside
- a bracket expression, a @b \ followed by an alphanumeric character merely stands
- for that character as an ordinary character, and inside a bracket expression,
- @b \ is an ordinary character. (The latter is the one actual incompatibility
- between EREs and AREs.)
- Character-entry escapes (AREs only) exist to make
- it easier to specify non-printing and otherwise inconvenient characters
- in REs:
-
-
-
-
-
-
- @b \a
-
-
-
-
- alert (bell) character, as in C
-
-
-
-
-
- @b \b
-
-
-
-
- backspace, as in C
-
-
-
-
-
- @b \B
-
-
-
-
- synonym
- for @b \ to help reduce backslash doubling in some applications where there
- are multiple levels of backslash processing
-
-
-
-
-
- @b \c@e X
-
-
-
-
- (where X is any character)
- the character whose low-order 5 bits are the same as those of @e X, and whose
- other bits are all zero
-
-
-
-
-
- @b \e
-
-
-
-
- the character whose collating-sequence name is
- '@b ESC', or failing that, the character with octal value 033
-
-
-
-
-
- @b \f
-
-
-
-
- formfeed, as in C
-
-
-
-
-
- @b \n
-
-
-
-
- newline, as in C
-
-
-
-
-
- @b \r
-
-
-
-
- carriage return, as in C
-
-
-
-
-
- @b \t
-
-
-
-
- horizontal tab, as in C
-
-
-
-
-
- @b \u@e wxyz
-
-
-
-
- (where @e wxyz is exactly four hexadecimal digits)
- the Unicode
- character @b U+@e wxyz in the local byte ordering
-
-
-
-
-
- @b \U@e stuvwxyz
-
-
-
-
- (where @e stuvwxyz is
- exactly eight hexadecimal digits) reserved for a somewhat-hypothetical Unicode
- extension to 32 bits
-
-
-
-
-
- @b \v
-
-
-
-
- vertical tab, as in C are all available.
-
-
-
-
-
- @b \x@e hhh
-
-
-
-
- (where
- @e hhh is any sequence of hexadecimal digits) the character whose hexadecimal
- value is @b 0x@e hhh (a single character no matter how many hexadecimal digits
- are used).
-
-
-
-
-
- @b \0
-
-
-
-
- the character whose value is @b 0
-
-
-
-
-
- @b \@e xy
-
-
-
-
- (where @e xy is exactly two
- octal digits, and is not a @e back reference (see below)) the character whose
- octal value is @b 0@e xy
-
-
-
-
-
- @b \@e xyz
-
-
-
-
- (where @e xyz is exactly three octal digits, and is
- not a back reference (see below))
- the character whose octal value is @b 0@e xyz
-
-
-
-
-
- Hexadecimal digits are '@b 0'-'@b 9', '@b a'-'@b f', and '@b A'-'@b F'. Octal
- digits are '@b 0'-'@b 7'.
- The character-entry
- escapes are always taken as ordinary characters. For example, @b \135 is @b ] in
- ASCII, but @b \135 does not terminate a bracket expression. Beware, however,
- that some applications (e.g., C compilers) interpret such sequences themselves
- before the regular-expression package gets to see them, which may require
- doubling (quadrupling, etc.) the '@b \'.
- Class-shorthand escapes (AREs only) provide
- shorthands for certain commonly-used character classes:
-
-
-
-
-
-
- @b \d
-
-
-
-
- @b [[:digit:]]
-
-
-
-
-
- @b \s
-
-
-
-
- @b [[:space:]]
-
-
-
-
-
- @b \w
-
-
-
-
- @b [[:alnum:]_] (note underscore)
-
-
-
-
-
- @b \D
-
-
-
-
- @b [^[:digit:]]
-
-
-
-
-
- @b \S
-
-
-
-
- @b [^[:space:]]
-
-
-
-
-
- @b \W
-
-
-
-
- @b [^[:alnum:]_] (note underscore)
-
-
-
-
-
- Within bracket expressions, '@b \d', '@b \s', and
- '@b \w' lose their outer brackets, and '@b \D',
- '@b \S', and '@b \W' are illegal. (So, for example,
- @b [a-c\d] is equivalent to @b [a-c[:digit:]].
- Also, @b [a-c\D], which is equivalent to
- @b [a-c^[:digit:]], is illegal.)
- A constraint escape (AREs only) is a constraint,
- matching the empty string if specific conditions are met, written as an
- escape:
-
-
-
-
-
-
- @b \A
-
-
-
-
- matches only at the beginning of the string
- (see #Matching, below,
- for how this differs from '@b ^')
-
-
-
-
-
- @b \m
-
-
-
-
- matches only at the beginning of a word
-
-
-
-
-
- @b \M
-
-
-
-
- matches only at the end of a word
-
-
-
-
-
- @b \y
-
-
-
-
- matches only at the beginning or end of a word
-
-
-
-
-
- @b \Y
-
-
-
-
- matches only at a point that is not the beginning or end of
- a word
-
-
-
-
-
- @b \Z
-
-
-
-
- matches only at the end of the string
- (see #Matching, below, for
- how this differs from '@b $')
-
-
-
-
-
- @b \@e m
-
-
-
-
- (where @e m is a nonzero digit) a @e back reference,
- see below
-
-
-
-
-
- @b \@e mnn
-
-
-
-
- (where @e m is a nonzero digit, and @e nn is some more digits,
- and the decimal value @e mnn is not greater than the number of closing capturing
- parentheses seen so far) a @e back reference, see below
-
-
-
-
-
- A word is defined
- as in the specification of @b [[::]] and @b [[::]] above. Constraint escapes are
- illegal within bracket expressions.
- A back reference (AREs only) matches
- the same string matched by the parenthesized subexpression specified by
- the number, so that (e.g.) @b ([bc])\1 matches @b bb or @b cc but not '@b bc'.
- The subexpression
- must entirely precede the back reference in the RE. Subexpressions are numbered
- in the order of their leading parentheses. Non-capturing parentheses do not
- define subexpressions.
- There is an inherent historical ambiguity between
- octal character-entry escapes and back references, which is resolved by
- heuristics, as hinted at above. A leading zero always indicates an octal
- escape. A single non-zero digit, not followed by another digit, is always
- taken as a back reference. A multi-digit sequence not starting with a zero
- is taken as a back reference if it comes after a suitable subexpression
- (i.e. the number is in the legal range for a back reference), and otherwise
- is taken as octal.
-
- @section remetasyntax Metasyntax
-
- @ref resyn_overview
- In addition to the main syntax described above,
- there are some special forms and miscellaneous syntactic facilities available.
- Normally the flavor of RE being used is specified by application-dependent
- means. However, this can be overridden by a @e director. If an RE of any flavor
- begins with '@b ***:', the rest of the RE is an ARE. If an RE of any flavor begins
- with '@b ***=', the rest of the RE is taken to be a literal string, with all
- characters considered ordinary characters.
- An ARE may begin with @e embedded options: a sequence @b (?xyz)
- (where @e xyz is one or more alphabetic characters)
- specifies options affecting the rest of the RE. These supplement, and can
- override, any options specified by the application. The available option
- letters are:
-
-
-
-
-
-
- @b b
-
-
-
-
- rest of RE is a BRE
-
-
-
-
-
- @b c
-
-
-
-
- case-sensitive matching (usual default)
-
-
-
-
-
- @b e
-
-
-
-
- rest of RE is an ERE
-
-
-
-
-
- @b i
-
-
-
-
- case-insensitive matching (see #Matching, below)
-
-
-
-
-
- @b m
-
-
-
-
- historical synonym for @b n
-
-
-
-
-
- @b n
-
-
-
-
- newline-sensitive matching (see #Matching, below)
-
-
-
-
-
- @b p
-
-
-
-
- partial newline-sensitive matching (see #Matching, below)
-
-
-
-
-
- @b q
-
-
-
-
- rest of RE
- is a literal ("quoted'') string, all ordinary characters
-
-
-
-
-
- @b s
-
-
-
-
- non-newline-sensitive matching (usual default)
-
-
-
-
-
- @b t
-
-
-
-
- tight syntax (usual default; see below)
-
-
-
-
-
- @b w
-
-
-
-
- inverse
- partial newline-sensitive ("weird'') matching (see #Matching, below)
-
-
-
-
-
- @b x
-
-
-
-
- expanded syntax (see below)
-
-
-
-
-
- Embedded options take effect at the @b ) terminating the
- sequence. They are available only at the start of an ARE, and may not be
- used later within it.
- In addition to the usual (@e tight) RE syntax, in which
- all characters are significant, there is an @e expanded syntax, available
- in AREs with the embedded
- x option. In the expanded syntax, white-space characters are ignored and
- all characters between a @b # and the following newline (or the end of the
- RE) are ignored, permitting paragraphing and commenting a complex RE. There
- are three exceptions to that basic rule:
-
-
- a white-space character or '@b #' preceded
- by '@b \' is retained
- white space or '@b #' within a bracket expression is retained
- white space and comments are illegal within multi-character symbols like
- the ARE '@b (?:' or the BRE '@b \('
-
-
- Expanded-syntax white-space characters are blank,
- tab, newline, and any character that belongs to the @e space character class.
- Finally, in an ARE, outside bracket expressions, the sequence '@b (?#ttt)' (where
- @e ttt is any text not containing a '@b )') is a comment, completely ignored. Again,
- this is not allowed between the characters of multi-character symbols like
- '@b (?:'. Such comments are more a historical artifact than a useful facility,
- and their use is deprecated; use the expanded syntax instead.
- @e None of these
- metasyntax extensions is available if the application (or an initial @b ***=
- director) has specified that the user's input be treated as a literal string
- rather than as an RE.
-
- @section wxresynmatching Matching
-
- @ref resyn_overview
- In the event that an RE could match more than
- one substring of a given string, the RE matches the one starting earliest
- in the string. If the RE could match more than one substring starting at
- that point, its choice is determined by its @e preference: either the longest
- substring, or the shortest.
- Most atoms, and all constraints, have no preference.
- A parenthesized RE has the same preference (possibly none) as the RE. A
- quantified atom with quantifier @b {m} or @b {m}? has the same preference (possibly
- none) as the atom itself. A quantified atom with other normal quantifiers
- (including @b {m,n} with @e m equal to @e n) prefers longest match. A quantified
- atom with other non-greedy quantifiers (including @b {m,n}? with @e m equal to
- @e n) prefers shortest match. A branch has the same preference as the first
- quantified atom in it which has a preference. An RE consisting of two or
- more branches connected by the @b | operator prefers longest match.
- Subject to the constraints imposed by the rules for matching the whole RE, subexpressions
- also match the longest or shortest possible substrings, based on their
- preferences, with subexpressions starting earlier in the RE taking priority
- over ones starting later. Note that outer subexpressions thus take priority
- over their component subexpressions.
- Note that the quantifiers @b {1,1} and
- @b {1,1}? can be used to force longest and shortest preference, respectively,
- on a subexpression or a whole RE.
- Match lengths are measured in characters,
- not collating elements. An empty string is considered longer than no match
- at all. For example, @b bb* matches the three middle characters
- of '@b abbbc', @b (week|wee)(night|knights)
- matches all ten characters of '@b weeknights', when @b (.*).* is matched against
- @b abc the parenthesized subexpression matches all three characters, and when
- @b (a*)* is matched against @b bc both the whole RE and the parenthesized subexpression
- match an empty string.
- If case-independent matching is specified, the effect
- is much as if all case distinctions had vanished from the alphabet. When
- an alphabetic that exists in multiple cases appears as an ordinary character
- outside a bracket expression, it is effectively transformed into a bracket
- expression containing both cases, so that @b x becomes '@b [xX]'. When it appears
- inside a bracket expression, all case counterparts of it are added to the
- bracket expression, so that @b [x] becomes @b [xX] and @b [^x] becomes '@b [^xX]'.
- If newline-sensitive
- matching is specified, @b . and bracket expressions using @b ^ will never match
- the newline character (so that matches will never cross newlines unless
- the RE explicitly arranges it) and @b ^ and @b $ will match the empty string after
- and before a newline respectively, in addition to matching at beginning
- and end of string respectively. ARE @b \A and @b \Z continue to match beginning
- or end of string @e only.
- If partial newline-sensitive matching is specified,
- this affects @b . and bracket expressions as with newline-sensitive matching,
- but not @b ^ and '@b $'.
- If inverse partial newline-sensitive matching is specified,
- this affects @b ^ and @b $ as with newline-sensitive matching, but not @b . and bracket
- expressions. This isn't very useful but is provided for symmetry.
-
- @section relimits Limits And Compatibility
-
- @ref resyn_overview
- No particular limit is imposed on the length of REs. Programs
- intended to be highly portable should not employ REs longer than 256 bytes,
- as a POSIX-compliant implementation can refuse to accept such REs.
- The only
- feature of AREs that is actually incompatible with POSIX EREs is that @b \
- does not lose its special significance inside bracket expressions. All other
- ARE features use syntax which is illegal or has undefined or unspecified
- effects in POSIX EREs; the @b *** syntax of directors likewise is outside
- the POSIX syntax for both BREs and EREs.
- Many of the ARE extensions are
- borrowed from Perl, but some have been changed to clean them up, and a
- few Perl extensions are not present. Incompatibilities of note include '@b \b',
- '@b \B', the lack of special treatment for a trailing newline, the addition of
- complemented bracket expressions to the things affected by newline-sensitive
- matching, the restrictions on parentheses and back references in lookahead
- constraints, and the longest/shortest-match (rather than first-match) matching
- semantics.
- The matching rules for REs containing both normal and non-greedy
- quantifiers have changed since early beta-test versions of this package.
- (The new rules are much simpler and cleaner, but don't work as hard at guessing
- the user's real intentions.)
- Henry Spencer's original 1986 @e regexp package, still in widespread use,
- implemented an early version of today's EREs. There are four incompatibilities between @e regexp's
- near-EREs ('RREs' for short) and AREs. In roughly increasing order of significance:
-
-
- In AREs, @b \ followed by an alphanumeric character is either an escape or
- an error, while in RREs, it was just another way of writing the alphanumeric.
- This should not be a problem because there was no reason to write such
- a sequence in RREs.
- @b { followed by a digit in an ARE is the beginning of
- a bound, while in RREs, @b { was always an ordinary character. Such sequences
- should be rare, and will often result in an error because following characters
- will not look like a valid bound.
- In AREs, @b \ remains a special character
- within '@b []', so a literal @b \ within @b [] must be
- written '@b \\'. @b \\ also gives a literal
- @b \ within @b [] in RREs, but only truly paranoid programmers routinely doubled
- the backslash.
- AREs report the longest/shortest match for the RE, rather
- than the first found in a specified search order. This may affect some RREs
- which were written in the expectation that the first match would be reported.
- (The careful crafting of RREs to optimize the search order for fast matching
- is obsolete (AREs examine all possible matches in parallel, and their performance
- is largely insensitive to their complexity) but cases where the search
- order was exploited to deliberately find a match which was @e not the longest/shortest
- will need rewriting.)
-
-
-
- @section wxresynbre Basic Regular Expressions
-
- @ref resyn_overview
- BREs differ from EREs in
- several respects. '@b |', '@b +', and @b ? are ordinary characters and there is no equivalent
- for their functionality. The delimiters for bounds
- are @b \{ and '@b \}', with @b { and
- @b } by themselves ordinary characters. The parentheses for nested subexpressions
- are @b \( and '@b \)', with @b ( and @b ) by themselves
- ordinary characters. @b ^ is an ordinary
- character except at the beginning of the RE or the beginning of a parenthesized
- subexpression, @b $ is an ordinary character except at the end of the RE or
- the end of a parenthesized subexpression, and @b * is an ordinary character
- if it appears at the beginning of the RE or the beginning of a parenthesized
- subexpression (after a possible leading '@b ^'). Finally, single-digit back references
- are available, and @b \ and @b \ are synonyms
- for @b [[::]] and @b [[::]] respectively;
- no other escapes are available.
-
- @section wxresynchars Regular Expression Character Names
-
- @ref resyn_overview
- Note that the character names are case sensitive.
-
-
-
-
-
-
- NUL
-
-
-
-
- '\0'
-
-
-
-
-
- SOH
-
-
-
-
- '\001'
-
-
-
-
-
- STX
-
-
-
-
- '\002'
-
-
-
-
-
- ETX
-
-
-
-
- '\003'
-
-
-
-
-
- EOT
-
-
-
-
- '\004'
-
-
-
-
-
- ENQ
-
-
-
-
- '\005'
-
-
-
-
-
- ACK
-
-
-
-
- '\006'
-
-
-
-
-
- BEL
-
-
-
-
- '\007'
-
-
-
-
-
- alert
-
-
-
-
- '\007'
-
-
-
-
-
- BS
-
-
-
-
- '\010'
-
-
-
-
-
- backspace
-
-
-
-
- '\b'
-
-
-
-
-
- HT
-
-
-
-
- '\011'
-
-
-
-
-
- tab
-
-
-
-
- '\t'
-
-
-
-
-
- LF
-
-
-
-
- '\012'
-
-
-
-
-
- newline
-
-
-
-
- '\n'
-
-
-
-
-
- VT
-
-
-
-
- '\013'
-
-
-
-
-
- vertical-tab
-
-
-
-
- '\v'
-
-
-
-
-
- FF
-
-
-
-
- '\014'
-
-
-
-
-
- form-feed
-
-
-
-
- '\f'
-
-
-
-
-
- CR
-
-
-
-
- '\015'
-
-
-
-
-
- carriage-return
-
-
-
-
- '\r'
-
-
-
-
-
- SO
-
-
-
-
- '\016'
-
-
-
-
-
- SI
-
-
-
-
- '\017'
-
-
-
-
-
- DLE
-
-
-
-
- '\020'
-
-
-
-
-
- DC1
-
-
-
-
- '\021'
-
-
-
-
-
- DC2
-
-
-
-
- '\022'
-
-
-
-
-
- DC3
-
-
-
-
- '\023'
-
-
-
-
-
- DC4
-
-
-
-
- '\024'
-
-
-
-
-
- NAK
-
-
-
-
- '\025'
-
-
-
-
-
- SYN
-
-
-
-
- '\026'
-
-
-
-
-
- ETB
-
-
-
-
- '\027'
-
-
-
-
-
- CAN
-
-
-
-
- '\030'
-
-
-
-
-
- EM
-
-
-
-
- '\031'
-
-
-
-
-
- SUB
-
-
-
-
- '\032'
-
-
-
-
-
- ESC
-
-
-
-
- '\033'
-
-
-
-
-
- IS4
-
-
-
-
- '\034'
-
-
-
-
-
- FS
-
-
-
-
- '\034'
-
-
-
-
-
- IS3
-
-
-
-
- '\035'
-
-
-
-
-
- GS
-
-
-
-
- '\035'
-
-
-
-
-
- IS2
-
-
-
-
- '\036'
-
-
-
-
-
- RS
-
-
-
-
- '\036'
-
-
-
-
-
- IS1
-
-
-
-
- '\037'
-
-
-
-
-
- US
-
-
-
-
- '\037'
-
-
-
-
-
- space
-
-
-
-
- ' '
-
-
-
-
-
- exclamation-mark
-
-
-
-
- '!'
-
-
-
-
-
- quotation-mark
-
-
-
-
- '"'
-
-
-
-
-
- number-sign
-
-
-
-
- '#'
-
-
-
-
-
- dollar-sign
-
-
-
-
- '$'
-
-
-
-
-
- percent-sign
-
-
-
-
- '%'
-
-
-
-
-
- ampersand
-
-
-
-
- ''
-
-
-
-
-
- apostrophe
-
-
-
-
- '\''
-
-
-
-
-
- left-parenthesis
-
-
-
-
- '('
-
-
-
-
-
- right-parenthesis
-
-
-
-
- ')'
-
-
-
-
-
- asterisk
-
-
-
-
- '*'
-
-
-
-
-
- plus-sign
-
-
-
-
- '+'
-
-
-
-
-
- comma
-
-
-
-
- ','
-
-
-
-
-
- hyphen
-
-
-
-
- '-'
-
-
-
-
-
- hyphen-minus
-
-
-
-
- '-'
-
-
-
-
-
- period
-
-
-
-
- '.'
-
-
-
-
-
- full-stop
-
-
-
-
- '.'
-
-
-
-
-
- slash
-
-
-
-
- '/'
-
-
-
-
-
- solidus
-
-
-
-
- '/'
-
-
-
-
-
- zero
-
-
-
-
- '0'
-
-
-
-
-
- one
-
-
-
-
- '1'
-
-
-
-
-
- two
-
-
-
-
- '2'
-
-
-
-
-
- three
-
-
-
-
- '3'
-
-
-
-
-
- four
-
-
-
-
- '4'
-
-
-
-
-
- five
-
-
-
-
- '5'
-
-
-
-
-
- six
-
-
-
-
- '6'
-
-
-
-
-
- seven
-
-
-
-
- '7'
-
-
-
-
-
- eight
-
-
-
-
- '8'
-
-
-
-
-
- nine
-
-
-
-
- '9'
-
-
-
-
-
- colon
-
-
-
-
- ':'
-
-
-
-
-
- semicolon
-
-
-
-
- ';'
-
-
-
-
-
- less-than-sign
-
-
-
-
- ''
-
-
-
-
-
- equals-sign
-
-
-
-
- '='
-
-
-
-
-
- greater-than-sign
-
-
-
-
- ''
-
-
-
-
-
- question-mark
-
-
-
-
- '?'
-
-
-
-
-
- commercial-at
-
-
-
-
- '@'
-
-
-
-
-
- left-square-bracket
-
-
-
-
- '['
-
-
-
-
-
- backslash
-
-
-
-
- '\'
-
-
-
-
-
- reverse-solidus
-
-
-
-
- '\'
-
-
-
-
-
- right-square-bracket
-
-
-
-
- ']'
-
-
-
-
-
- circumflex
-
-
-
-
- '^'
-
-
-
-
-
- circumflex-accent
-
-
-
-
- '^'
-
-
-
-
-
- underscore
-
-
-
-
- '_'
-
-
-
-
-
- low-line
-
-
-
-
- '_'
-
-
-
-
-
- grave-accent
-
-
-
-
- '''
-
-
-
-
-
- left-brace
-
-
-
-
- '{'
-
-
-
-
-
- left-curly-bracket
-
-
-
-
- '{'
-
-
-
-
-
- vertical-line
-
-
-
-
- '|'
-
-
-
-
-
- right-brace
-
-
-
-
- '}'
-
-
-
-
-
- right-curly-bracket
-
-
-
-
- '}'
-
-
-
-
-
- tilde
-
-
-
-
- '~'
-
-
-
-
-
- DEL
-
-
-
-
- '\177'
-
- */
-
+/**
+
+@page overview_resyntax Regular Expressions
+
+A <em>regular expression</em> describes strings of characters. It's a pattern
+that matches certain strings and doesn't match others.
+
+@li @ref overview_resyntax_differentflavors
+@li @ref overview_resyntax_syntax
+@li @ref overview_resyntax_bracket
+@li @ref overview_resyntax_escapes
+@li @ref overview_resyntax_metasyntax
+@li @ref overview_resyntax_matching
+@li @ref overview_resyntax_limits
+@li @ref overview_resyntax_bre
+@li @ref overview_resyntax_characters
+
+@see
+
+@li wxRegEx
+
+
+<hr>
+
+
+@section overview_resyntax_differentflavors Different Flavors of Regular Expressions
+
+Regular expressions (RE), as defined by POSIX, come in two flavors:
+<em>extended regular expressions</em> (ERE) and <em>basic regular
+expressions</em> (BRE). EREs are roughly those of the traditional @e egrep,
+while BREs are roughly those of the traditional @e ed. This implementation
+adds a third flavor: <em>advanced regular expressions</em> (ARE), basically
+EREs with some significant extensions.
+
+This manual page primarily describes AREs. BREs mostly exist for backward
+compatibility in some old programs. POSIX EREs are almost an exact subset of
+AREs. Features of AREs that are not present in EREs will be indicated.
+
+
+@section overview_resyntax_syntax Regular Expression Syntax
+
+These regular expressions are implemented using the package written by Henry
+Spencer, based on the 1003.2 spec and some (not quite all) of the Perl5
+extensions (thanks, Henry!). Much of the description of regular expressions
+below is copied verbatim from his manual entry.
+
+An ARE is one or more @e branches, separated by "|", matching anything that
+matches any of the branches.
+
+A branch is zero or more @e constraints or @e quantified atoms, concatenated.
+It matches a match for the first, followed by a match for the second, etc; an
+empty branch matches the empty string.
+
+A quantified atom is an @e atom possibly followed by a single @e quantifier.
+Without a quantifier, it matches a match for the atom. The quantifiers, and
+what a so-quantified atom matches, are:
+
+@beginTable
+@row2col{ <tt>*</tt> ,
+ A sequence of 0 or more matches of the atom. }
+@row2col{ <tt>+</tt> ,
+ A sequence of 1 or more matches of the atom. }
+@row2col{ <tt>?</tt> ,
+ A sequence of 0 or 1 matches of the atom. }
+@row2col{ <tt>{m}</tt> ,
+ A sequence of exactly @e m matches of the atom. }
+@row2col{ <tt>{m\,}</tt> ,
+ A sequence of @e m or more matches of the atom. }
+@row2col{ <tt>{m\,n}</tt> ,
+ A sequence of @e m through @e n (inclusive) matches of the atom; @e m may
+ not exceed @e n. }
+@row2col{ <tt>*? +? ?? {m}? {m\,}? {m\,n}?</tt> ,
+ @e Non-greedy quantifiers, which match the same possibilities, but prefer
+ the smallest number rather than the largest number of matches (see
+ @ref overview_resyntax_matching). }
+@endTable
+
+The forms using @b { and @b } are known as @e bounds. The numbers @e m and
+@e n are unsigned decimal integers with permissible values from 0 to 255
+inclusive. An atom is one of:
+
+@beginTable
+@row2col{ <tt>(re)</tt> ,
+ Where @e re is any regular expression, matches for @e re, with the match
+ captured for possible reporting. }
+@row2col{ <tt>(?:re)</tt> ,
+ As previous, but does no reporting (a "non-capturing" set of
+ parentheses). }
+@row2col{ <tt>()</tt> ,
+ Matches an empty string, captured for possible reporting. }
+@row2col{ <tt>(?:)</tt> ,
+ Matches an empty string, without reporting. }
+@row2col{ <tt>[chars]</tt> ,
+ A <em>bracket expression</em>, matching any one of the @e chars (see
+ @ref overview_resyntax_bracket for more details). }
+@row2col{ <tt>.</tt> ,
+ Matches any single character. }
+@row2col{ <tt>@\k</tt> ,
+ Where @e k is a non-alphanumeric character, matches that character taken
+ as an ordinary character, e.g. @\@\ matches a backslash character. }
+@row2col{ <tt>@\c</tt> ,
+ Where @e c is alphanumeric (possibly followed by other characters), an
+ @e escape (AREs only), see @ref overview_resyntax_escapes below. }
+@row2col{ <tt>@leftCurly</tt> ,
+ When followed by a character other than a digit, matches the left-brace
+ character "@leftCurly"; when followed by a digit, it is the beginning of a
+ @e bound (see above). }
+@row2col{ <tt>x</tt> ,
+ Where @e x is a single character with no other significance, matches that
+ character. }
+@endTable
+
+A @e constraint matches an empty string when specific conditions are met. A
+constraint may not be followed by a quantifier. The simple constraints are as
+follows; some more constraints are described later, under
+@ref overview_resyntax_escapes.
+
+@beginTable
+@row2col{ <tt>^</tt> ,
+ Matches at the beginning of a line. }
+@row2col{ <tt>@$</tt> ,
+ Matches at the end of a line. }
+@row2col{ <tt>(?=re)</tt> ,
+ @e Positive lookahead (AREs only), matches at any point where a substring
+ matching @e re begins. }
+@row2col{ <tt>(?!re)</tt> ,
+ @e Negative lookahead (AREs only), matches at any point where no substring
+ matching @e re begins. }
+@endTable
+
+The lookahead constraints may not contain back references (see later), and all
+parentheses within them are considered non-capturing. A RE may not end with
+"\".
+
+
+@section overview_resyntax_bracket Bracket Expressions
+
+A <em>bracket expression</em> is a list of characters enclosed in <tt>[]</tt>.
+It normally matches any single character from the list (but see below). If the
+list begins with @c ^, it matches any single character (but see below) @e not
+from the rest of the list.
+
+If two characters in the list are separated by <tt>-</tt>, this is shorthand
+for the full @e range of characters between those two (inclusive) in the
+collating sequence, e.g. <tt>[0-9]</tt> in ASCII matches any decimal digit.
+Two ranges may not share an endpoint, so e.g. <tt>a-c-e</tt> is illegal.
+Ranges are very collating-sequence-dependent, and portable programs should
+avoid relying on them.
+
+To include a literal <tt>]</tt> or <tt>-</tt> in the list, the simplest method
+is to enclose it in <tt>[.</tt> and <tt>.]</tt> to make it a collating element
+(see below). Alternatively, make it the first character (following a possible
+<tt>^</tt>), or (AREs only) precede it with <tt>@\</tt>. Alternatively, for
+<tt>-</tt>, make it the last character, or the second endpoint of a range. To
+use a literal <tt>-</tt> as the first endpoint of a range, make it a collating
+element or (AREs only) precede it with <tt>@\</tt>. With the exception of
+these, some combinations using <tt>[</tt> (see next paragraphs), and escapes,
+all other special characters lose their special significance within a bracket
+expression.
+
+Within a bracket expression, a collating element (a character, a
+multi-character sequence that collates as if it were a single character, or a
+collating-sequence name for either) enclosed in <tt>[.</tt> and <tt>.]</tt>
+stands for the sequence of characters of that collating element.
+
+@e wxWidgets: Currently no multi-character collating elements are defined. So
+in <tt>[.X.]</tt>, @c X can either be a single character literal or the name
+of a character. For example, the following are both identical:
+<tt>[[.0.]-[.9.]]</tt> and <tt>[[.zero.]-[.nine.]]</tt> and mean the same as
+<tt>[0-9]</tt>. See @ref overview_resyntax_characters.
+
+Within a bracket expression, a collating element enclosed in <tt>[=</tt> and
+<tt>=]</tt> is an equivalence class, standing for the sequences of characters
+of all collating elements equivalent to that one, including itself. An
+equivalence class may not be an endpoint of a range.
+
+@e wxWidgets: Currently no equivalence classes are defined, so <tt>[=X=]</tt>
+stands for just the single character @c X. @c X can either be a single
+character literal or the name of a character, see
+@ref overview_resyntax_characters.
+
+Within a bracket expression, the name of a @e character class enclosed in
+<tt>[:</tt> and <tt>:]</tt> stands for the list of all characters (not all
+collating elements!) belonging to that class. Standard character classes are:
+
+@beginTable
+@row2col{ <tt>alpha</tt> , A letter. }
+@row2col{ <tt>upper</tt> , An upper-case letter. }
+@row2col{ <tt>lower</tt> , A lower-case letter. }
+@row2col{ <tt>digit</tt> , A decimal digit. }
+@row2col{ <tt>xdigit</tt> , A hexadecimal digit. }
+@row2col{ <tt>alnum</tt> , An alphanumeric (letter or digit). }
+@row2col{ <tt>print</tt> , An alphanumeric (same as alnum). }
+@row2col{ <tt>blank</tt> , A space or tab character. }
+@row2col{ <tt>space</tt> , A character producing white space in displayed text. }
+@row2col{ <tt>punct</tt> , A punctuation character. }
+@row2col{ <tt>graph</tt> , A character with a visible representation. }
+@row2col{ <tt>cntrl</tt> , A control character. }
+@endTable
+
+A character class may not be used as an endpoint of a range.
+
+@e wxWidgets: In a non-Unicode build, these character classifications depend on
+the current locale, and correspond to the values return by the ANSI C "is"
+functions: <tt>isalpha</tt>, <tt>isupper</tt>, etc. In Unicode mode they are
+based on Unicode classifications, and are not affected by the current locale.
+
+There are two special cases of bracket expressions: the bracket expressions
+<tt>[[:@<:]]</tt> and <tt>[[:@>:]]</tt> are constraints, matching empty strings at
+the beginning and end of a word respectively. A word is defined as a sequence
+of word characters that is neither preceded nor followed by word characters. A
+word character is an @e alnum character or an underscore (_). These special
+bracket expressions are deprecated; users of AREs should use constraint escapes
+instead (see escapes below).
+
+
+@section overview_resyntax_escapes Escapes
+
+Escapes (AREs only), which begin with a <tt>@\</tt> followed by an alphanumeric
+character, come in several varieties: character entry, class shorthands,
+constraint escapes, and back references. A <tt>@\</tt> followed by an
+alphanumeric character but not constituting a valid escape is illegal in AREs.
+In EREs, there are no escapes: outside a bracket expression, a <tt>@\</tt>
+followed by an alphanumeric character merely stands for that character as an
+ordinary character, and inside a bracket expression, <tt>@\</tt> is an ordinary
+character. (The latter is the one actual incompatibility between EREs and
+AREs.)
+
+Character-entry escapes (AREs only) exist to make it easier to specify
+non-printing and otherwise inconvenient characters in REs:
+
+@beginTable
+@row2col{ <tt>@\a</tt> , Alert (bell) character, as in C. }
+@row2col{ <tt>@\b</tt> , Backspace, as in C. }
+@row2col{ <tt>@\B</tt> ,
+ Synonym for <tt>@\</tt> to help reduce backslash doubling in some
+ applications where there are multiple levels of backslash processing. }
+@row2col{ <tt>@\cX</tt> ,
+ The character whose low-order 5 bits are the same as those of @e X, and
+ whose other bits are all zero, where @e X is any character. }
+@row2col{ <tt>@\e</tt> ,
+ The character whose collating-sequence name is @c ESC, or failing that,
+ the character with octal value 033. }
+@row2col{ <tt>@\f</tt> , Formfeed, as in C. }
+@row2col{ <tt>@\n</tt> , Newline, as in C. }
+@row2col{ <tt>@\r</tt> , Carriage return, as in C. }
+@row2col{ <tt>@\t</tt> , Horizontal tab, as in C. }
+@row2col{ <tt>@\uwxyz</tt> ,
+ The Unicode character <tt>U+wxyz</tt> in the local byte ordering, where
+ @e wxyz is exactly four hexadecimal digits. }
+@row2col{ <tt>@\Ustuvwxyz</tt> ,
+ Reserved for a somewhat-hypothetical Unicode extension to 32 bits, where
+ @e stuvwxyz is exactly eight hexadecimal digits. }
+@row2col{ <tt>@\v</tt> , Vertical tab, as in C are all available. }
+@row2col{ <tt>@\xhhh</tt> ,
+ The single character whose hexadecimal value is @e 0xhhh, where @e hhh is
+ any sequence of hexadecimal digits. }
+@row2col{ <tt>@\0</tt> , The character whose value is 0. }
+@row2col{ <tt>@\xy</tt> ,
+ The character whose octal value is @e 0xy, where @e xy is exactly two octal
+ digits, and is not a <em>back reference</em> (see below). }
+@row2col{ <tt>@\xyz</tt> ,
+ The character whose octal value is @e 0xyz, where @e xyz is exactly three
+ octal digits, and is not a <em>back reference</em> (see below). }
+@endTable
+
+Hexadecimal digits are 0-9, a-f, and A-F. Octal digits are 0-7.
+
+The character-entry escapes are always taken as ordinary characters. For
+example, <tt>@\135</tt> is <tt>]</tt> in ASCII, but <tt>@\135</tt> does not
+terminate a bracket expression. Beware, however, that some applications (e.g.,
+C compilers) interpret such sequences themselves before the regular-expression
+package gets to see them, which may require doubling (quadrupling, etc.) the
+'<tt>@\</tt>'.
+
+Class-shorthand escapes (AREs only) provide shorthands for certain
+commonly-used character classes:
+
+@beginTable
+@row2col{ <tt>@\d</tt> , <tt>[[:digit:]]</tt> }
+@row2col{ <tt>@\s</tt> , <tt>[[:space:]]</tt> }
+@row2col{ <tt>@\w</tt> , <tt>[[:alnum:]_]</tt> (note underscore) }
+@row2col{ <tt>@\D</tt> , <tt>[^[:digit:]]</tt> }
+@row2col{ <tt>@\S</tt> , <tt>[^[:space:]]</tt> }
+@row2col{ <tt>@\W</tt> , <tt>[^[:alnum:]_]</tt> (note underscore) }
+@endTable
+
+Within bracket expressions, <tt>@\d</tt>, <tt>@\s</tt>, and <tt>@\w</tt> lose
+their outer brackets, and <tt>@\D</tt>, <tt>@\S</tt>, <tt>@\W</tt> are illegal.
+So, for example, <tt>[a-c@\d]</tt> is equivalent to <tt>[a-c[:digit:]]</tt>.
+Also, <tt>[a-c@\D]</tt>, which is equivalent to <tt>[a-c^[:digit:]]</tt>, is
+illegal.
+
+A constraint escape (AREs only) is a constraint, matching the empty string if
+specific conditions are met, written as an escape:
+
+@beginTable
+@row2col{ <tt>@\A</tt> , Matches only at the beginning of the string, see
+ @ref overview_resyntax_matching for how this differs
+ from <tt>^</tt>. }
+@row2col{ <tt>@\m</tt> , Matches only at the beginning of a word. }
+@row2col{ <tt>@\M</tt> , Matches only at the end of a word. }
+@row2col{ <tt>@\y</tt> , Matches only at the beginning or end of a word. }
+@row2col{ <tt>@\Y</tt> , Matches only at a point that is not the beginning or
+ end of a word. }
+@row2col{ <tt>@\Z</tt> , Matches only at the end of the string, see
+ @ref overview_resyntax_matching for how this differs
+ from <tt>@$</tt>. }
+@row2col{ <tt>@\m</tt> , A <em>back reference</em>, where @e m is a non-zero
+ digit. See below. }
+@row2col{ <tt>@\mnn</tt> ,
+ A <em>back reference</em>, where @e m is a nonzero digit, and @e nn is some
+ more digits, and the decimal value @e mnn is not greater than the number of
+ closing capturing parentheses seen so far. See below. }
+@endTable
+
+A word is defined as in the specification of <tt>[[:@<:]]</tt> and
+<tt>[[:@>:]]</tt> above. Constraint escapes are illegal within bracket
+expressions.
+
+A back reference (AREs only) matches the same string matched by the
+parenthesized subexpression specified by the number. For example, "([bc])\1"
+matches "bb" or "cc" but not "bc". The subexpression must entirely precede the
+back reference in the RE.Subexpressions are numbered in the order of their
+leading parentheses. Non-capturing parentheses do not define subexpressions.
+
+There is an inherent historical ambiguity between octal character-entry escapes
+and back references, which is resolved by heuristics, as hinted at above. A
+leading zero always indicates an octal escape. A single non-zero digit, not
+followed by another digit, is always taken as a back reference. A multi-digit
+sequence not starting with a zero is taken as a back reference if it comes
+after a suitable subexpression (i.e. the number is in the legal range for a
+back reference), and otherwise is taken as octal.
+
+
+@section overview_resyntax_metasyntax Metasyntax
+
+In addition to the main syntax described above, there are some special forms
+and miscellaneous syntactic facilities available.
+
+Normally the flavor of RE being used is specified by application-dependent
+means. However, this can be overridden by a @e director. If an RE of any flavor
+begins with <tt>***:</tt>, the rest of the RE is an ARE. If an RE of any
+flavor begins with <tt>***=</tt>, the rest of the RE is taken to be a literal
+string, with all characters considered ordinary characters.
+
+An ARE may begin with <em>embedded options</em>: a sequence <tt>(?xyz)</tt>
+(where @e xyz is one or more alphabetic characters) specifies options affecting
+the rest of the RE. These supplement, and can override, any options specified
+by the application. The available option letters are:
+
+@beginTable
+@row2col{ <tt>b</tt> , Rest of RE is a BRE. }
+@row2col{ <tt>c</tt> , Case-sensitive matching (usual default). }
+@row2col{ <tt>e</tt> , Rest of RE is an ERE. }
+@row2col{ <tt>i</tt> , Case-insensitive matching (see
+ @ref overview_resyntax_matching, below). }
+@row2col{ <tt>m</tt> , Historical synonym for @e n. }
+@row2col{ <tt>n</tt> , Newline-sensitive matching (see
+ @ref overview_resyntax_matching, below). }
+@row2col{ <tt>p</tt> , Partial newline-sensitive matching (see
+ @ref overview_resyntax_matching, below). }
+@row2col{ <tt>q</tt> , Rest of RE is a literal ("quoted") string, all ordinary
+ characters. }
+@row2col{ <tt>s</tt> , Non-newline-sensitive matching (usual default). }
+@row2col{ <tt>t</tt> , Tight syntax (usual default; see below). }
+@row2col{ <tt>w</tt> , Inverse partial newline-sensitive ("weird") matching
+ (see @ref overview_resyntax_matching, below). }
+@row2col{ <tt>x</tt> , Expanded syntax (see below). }
+@endTable
+
+Embedded options take effect at the <tt>)</tt> terminating the sequence. They
+are available only at the start of an ARE, and may not be used later within it.
+
+In addition to the usual (@e tight) RE syntax, in which all characters are
+significant, there is an @e expanded syntax, available in AREs with the
+embedded x option. In the expanded syntax, white-space characters are ignored
+and all characters between a <tt>@#</tt> and the following newline (or the end
+of the RE) are ignored, permitting paragraphing and commenting a complex RE.
+There are three exceptions to that basic rule:
+
+@li A white-space character or <tt>@#</tt> preceded by <tt>@\</tt> is retained.
+@li White space or <tt>@#</tt> within a bracket expression is retained.
+@li White space and comments are illegal within multi-character symbols like
+ the ARE <tt>(?:</tt> or the BRE <tt>\(</tt>.
+
+Expanded-syntax white-space characters are blank, tab, newline, and any
+character that belongs to the @e space character class.
+
+Finally, in an ARE, outside bracket expressions, the sequence <tt>(?@#ttt)</tt>
+(where @e ttt is any text not containing a <tt>)</tt>) is a comment, completely
+ignored. Again, this is not allowed between the characters of multi-character
+symbols like <tt>(?:</tt>. Such comments are more a historical artifact than a
+useful facility, and their use is deprecated; use the expanded syntax instead.
+
+@e None of these metasyntax extensions is available if the application (or an
+initial <tt>***=</tt> director) has specified that the user's input be treated
+as a literal string rather than as an RE.
+
+
+@section overview_resyntax_matching Matching
+
+In the event that an RE could match more than one substring of a given string,
+the RE matches the one starting earliest in the string. If the RE could match
+more than one substring starting at that point, the choice is determined by
+it's @e preference: either the longest substring, or the shortest.
+
+Most atoms, and all constraints, have no preference. A parenthesized RE has the
+same preference (possibly none) as the RE. A quantified atom with quantifier
+<tt>{m}</tt> or <tt>{m}?</tt> has the same preference (possibly none) as the
+atom itself. A quantified atom with other normal quantifiers (including
+<tt>{m,n}</tt> with @e m equal to @e n) prefers longest match. A quantified
+atom with other non-greedy quantifiers (including <tt>{m,n}?</tt> with @e m
+equal to @e n) prefers shortest match. A branch has the same preference as the
+first quantified atom in it which has a preference. An RE consisting of two or
+more branches connected by the @c | operator prefers longest match.
+
+Subject to the constraints imposed by the rules for matching the whole RE,
+subexpressions also match the longest or shortest possible substrings, based on
+their preferences, with subexpressions starting earlier in the RE taking
+priority over ones starting later. Note that outer subexpressions thus take
+priority over their component subexpressions.
+
+Note that the quantifiers <tt>{1,1}</tt> and <tt>{1,1}?</tt> can be used to
+force longest and shortest preference, respectively, on a subexpression or a
+whole RE.
+
+Match lengths are measured in characters, not collating elements. An empty
+string is considered longer than no match at all. For example, <tt>bb*</tt>
+matches the three middle characters of "abbbc",
+<tt>(week|wee)(night|knights)</tt> matches all ten characters of "weeknights",
+when <tt>(.*).*</tt> is matched against "abc" the parenthesized subexpression
+matches all three characters, and when <tt>(a*)*</tt> is matched against "bc"
+both the whole RE and the parenthesized subexpression match an empty string.
+
+If case-independent matching is specified, the effect is much as if all case
+distinctions had vanished from the alphabet. When an alphabetic that exists in
+multiple cases appears as an ordinary character outside a bracket expression,
+it is effectively transformed into a bracket expression containing both cases,
+so that @c x becomes @c [xX]. When it appears inside a bracket expression, all
+case counterparts of it are added to the bracket expression, so that @c [x]
+becomes @c [xX] and @c [^x] becomes @c [^xX].
+
+If newline-sensitive matching is specified, "." and bracket expressions using
+"^" will never match the newline character (so that matches will never cross
+newlines unless the RE explicitly arranges it) and "^" and "$" will match the
+empty string after and before a newline respectively, in addition to matching
+at beginning and end of string respectively. ARE <tt>@\A</tt> and <tt>@\Z</tt>
+continue to match beginning or end of string @e only.
+
+If partial newline-sensitive matching is specified, this affects "." and
+bracket expressions as with newline-sensitive matching, but not "^" and "$".
+
+If inverse partial newline-sensitive matching is specified, this affects "^"
+and "$" as with newline-sensitive matching, but not "." and bracket
+expressions. This isn't very useful but is provided for symmetry.
+
+
+@section overview_resyntax_limits Limits and Compatibility
+
+No particular limit is imposed on the length of REs. Programs intended to be
+highly portable should not employ REs longer than 256 bytes, as a
+POSIX-compliant implementation can refuse to accept such REs.
+
+The only feature of AREs that is actually incompatible with POSIX EREs is that
+<tt>@\</tt> does not lose its special significance inside bracket expressions.
+All other ARE features use syntax which is illegal or has undefined or
+unspecified effects in POSIX EREs; the <tt>***</tt> syntax of directors
+likewise is outside the POSIX syntax for both BREs and EREs.
+
+Many of the ARE extensions are borrowed from Perl, but some have been changed
+to clean them up, and a few Perl extensions are not present. Incompatibilities
+of note include <tt>@\b</tt>, <tt>@\B</tt>, the lack of special treatment for a
+trailing newline, the addition of complemented bracket expressions to the
+things affected by newline-sensitive matching, the restrictions on parentheses
+and back references in lookahead constraints, and the longest/shortest-match
+(rather than first-match) matching semantics.
+
+The matching rules for REs containing both normal and non-greedy quantifiers
+have changed since early beta-test versions of this package. The new rules are
+much simpler and cleaner, but don't work as hard at guessing the user's real
+intentions.
+
+Henry Spencer's original 1986 @e regexp package, still in widespread use,
+implemented an early version of today's EREs. There are four incompatibilities
+between @e regexp's near-EREs (RREs for short) and AREs. In roughly increasing
+order of significance:
+
+@li In AREs, <tt>@\</tt> followed by an alphanumeric character is either an
+ escape or an error, while in RREs, it was just another way of writing the
+ alphanumeric. This should not be a problem because there was no reason to
+ write such a sequence in RREs.
+@li @c { followed by a digit in an ARE is the beginning of a bound, while in
+ RREs, @c { was always an ordinary character. Such sequences should be rare,
+ and will often result in an error because following characters will not
+ look like a valid bound.
+@li In AREs, @c @\ remains a special character within @c [], so a literal @c @\
+ within @c [] must be written as <tt>@\@\</tt>. <tt>@\@\</tt> also gives a
+ literal @c @\ within @c [] in RREs, but only truly paranoid programmers
+ routinely doubled the backslash.
+@li AREs report the longest/shortest match for the RE, rather than the first
+ found in a specified search order. This may affect some RREs which were
+ written in the expectation that the first match would be reported. The
+ careful crafting of RREs to optimize the search order for fast matching is
+ obsolete (AREs examine all possible matches in parallel, and their
+ performance is largely insensitive to their complexity) but cases where the
+ search order was exploited to deliberately find a match which was @e not
+ the longest/shortest will need rewriting.
+
+
+@section overview_resyntax_bre Basic Regular Expressions
+
+BREs differ from EREs in several respects. @c |, @c +, and @c ? are ordinary
+characters and there is no equivalent for their functionality. The delimiters
+for bounds are @c @\{ and @c @\}, with @c { and @c } by themselves ordinary
+characters. The parentheses for nested subexpressions are @c @\( and @c @\),
+with @c ( and @c ) by themselves ordinary characters. @c ^ is an ordinary
+character except at the beginning of the RE or the beginning of a parenthesized
+subexpression, @c $ is an ordinary character except at the end of the RE or the
+end of a parenthesized subexpression, and @c * is an ordinary character if it
+appears at the beginning of the RE or the beginning of a parenthesized
+subexpression (after a possible leading <tt>^</tt>). Finally, single-digit back
+references are available, and @c @\@< and @c @\@> are synonyms for
+<tt>[[:@<:]]</tt> and <tt>[[:@>:]]</tt> respectively; no other escapes are
+available.
+
+
+@section overview_resyntax_characters Regular Expression Character Names
+
+Note that the character names are case sensitive.
+
+<center><table class='doctable' border='0' cellspacing='5' cellpadding='4'><tr>
+
+<td>
+@beginTable
+@row2col{ <tt>NUL</tt> , @\0 }
+@row2col{ <tt>SOH</tt> , @\001 }
+@row2col{ <tt>STX</tt> , @\002 }
+@row2col{ <tt>ETX</tt> , @\003 }
+@row2col{ <tt>EOT</tt> , @\004 }
+@row2col{ <tt>ENQ</tt> , @\005 }
+@row2col{ <tt>ACK</tt> , @\006 }
+@row2col{ <tt>BEL</tt> , @\007 }
+@row2col{ <tt>alert</tt> , @\007 }
+@row2col{ <tt>BS</tt> , @\010 }
+@row2col{ <tt>backspace</tt> , @\b }
+@row2col{ <tt>HT</tt> , @\011 }
+@row2col{ <tt>tab</tt> , @\t }
+@row2col{ <tt>LF</tt> , @\012 }
+@row2col{ <tt>newline</tt> , @\n }
+@row2col{ <tt>VT</tt> , @\013 }
+@row2col{ <tt>vertical-tab</tt> , @\v }
+@row2col{ <tt>FF</tt> , @\014 }
+@row2col{ <tt>form-feed</tt> , @\f }
+@endTable
+</td>
+
+<td>
+@beginTable
+@row2col{ <tt>CR</tt> , @\015 }
+@row2col{ <tt>carriage-return</tt> , @\r }
+@row2col{ <tt>SO</tt> , @\016 }
+@row2col{ <tt>SI</tt> , @\017 }
+@row2col{ <tt>DLE</tt> , @\020 }
+@row2col{ <tt>DC1</tt> , @\021 }
+@row2col{ <tt>DC2</tt> , @\022 }
+@row2col{ <tt>DC3</tt> , @\023 }
+@row2col{ <tt>DC4</tt> , @\024 }
+@row2col{ <tt>NAK</tt> , @\025 }
+@row2col{ <tt>SYN</tt> , @\026 }
+@row2col{ <tt>ETB</tt> , @\027 }
+@row2col{ <tt>CAN</tt> , @\030 }
+@row2col{ <tt>EM</tt> , @\031 }
+@row2col{ <tt>SUB</tt> , @\032 }
+@row2col{ <tt>ESC</tt> , @\033 }
+@row2col{ <tt>IS4</tt> , @\034 }
+@row2col{ <tt>FS</tt> , @\034 }
+@row2col{ <tt>IS3</tt> , @\035 }
+@endTable
+</td>
+
+<td>
+@beginTable
+@row2col{ <tt>GS</tt> , @\035 }
+@row2col{ <tt>IS2</tt> , @\036 }
+@row2col{ <tt>RS</tt> , @\036 }
+@row2col{ <tt>IS1</tt> , @\037 }
+@row2col{ <tt>US</tt> , @\037 }
+@row2col{ <tt>space</tt> , " " (space) }
+@row2col{ <tt>exclamation-mark</tt> , ! }
+@row2col{ <tt>quotation-mark</tt> , " }
+@row2col{ <tt>number-sign</tt> , @# }
+@row2col{ <tt>dollar-sign</tt> , @$ }
+@row2col{ <tt>percent-sign</tt> , @% }
+@row2col{ <tt>ampersand</tt> , @& }
+@row2col{ <tt>apostrophe</tt> , ' }
+@row2col{ <tt>left-parenthesis</tt> , ( }
+@row2col{ <tt>right-parenthesis</tt> , ) }
+@row2col{ <tt>asterisk</tt> , * }
+@row2col{ <tt>plus-sign</tt> , + }
+@row2col{ <tt>comma</tt> , \, }
+@row2col{ <tt>hyphen</tt> , - }
+@endTable
+</td>
+
+<td>
+@beginTable
+@row2col{ <tt>hyphen-minus</tt> , - }
+@row2col{ <tt>period</tt> , . }
+@row2col{ <tt>full-stop</tt> , . }
+@row2col{ <tt>slash</tt> , / }
+@row2col{ <tt>solidus</tt> , / }
+@row2col{ <tt>zero</tt> , 0 }
+@row2col{ <tt>one</tt> , 1 }
+@row2col{ <tt>two</tt> , 2 }
+@row2col{ <tt>three</tt> , 3 }
+@row2col{ <tt>four</tt> , 4 }
+@row2col{ <tt>five</tt> , 5 }
+@row2col{ <tt>six</tt> , 6 }
+@row2col{ <tt>seven</tt> , 7 }
+@row2col{ <tt>eight</tt> , 8 }
+@row2col{ <tt>nine</tt> , 9 }
+@row2col{ <tt>colon</tt> , : }
+@row2col{ <tt>semicolon</tt> , ; }
+@row2col{ <tt>less-than-sign</tt> , @< }
+@row2col{ <tt>equals-sign</tt> , = }
+@endTable
+</td>
+
+<td>
+@beginTable
+@row2col{ <tt>greater-than-sign</tt> , @> }
+@row2col{ <tt>question-mark</tt> , ? }
+@row2col{ <tt>commercial-at</tt> , @@ }
+@row2col{ <tt>left-square-bracket</tt> , [ }
+@row2col{ <tt>backslash</tt> , @\ }
+@row2col{ <tt>reverse-solidus</tt> , @\ }
+@row2col{ <tt>right-square-bracket</tt> , ] }
+@row2col{ <tt>circumflex</tt> , ^ }
+@row2col{ <tt>circumflex-accent</tt> , ^ }
+@row2col{ <tt>underscore</tt> , _ }
+@row2col{ <tt>low-line</tt> , _ }
+@row2col{ <tt>grave-accent</tt> , ' }
+@row2col{ <tt>left-brace</tt> , @leftCurly }
+@row2col{ <tt>left-curly-bracket</tt> , @leftCurly }
+@row2col{ <tt>vertical-line</tt> , | }
+@row2col{ <tt>right-brace</tt> , @rightCurly }
+@row2col{ <tt>right-curly-bracket</tt> , @rightCurly }
+@row2col{ <tt>tilde</tt> , ~ }
+@row2col{ <tt>DEL</tt> , @\177 }
+@endTable
+</td>
+
+</tr></table></center>
+
+*/
projects / wxWidgets.git / blobdiff