Splits a string based on a regular expression. The regular expression should identify one delimiter.
This does not advance and produces an infinite list of  if the regex matches an empty string. This misfeature is here to match the behavior of the the original Text.Regex API.
Replaces every occurance of the given regexp with the replacement string.
In the replacement string,
"\1" refers to the first substring;
"\2" to the second, etc; and
"\0" to the entire match.
"\\\\" will insert a literal backslash.
This does not advance if the regex matches an empty string. This misfeature is here to match the behavior of the the original Text.Regex API.
Classes and instances for Regex matching.
To see what result types the instances of RegexContext can produce, please read the Text.Regex.Base.Context haddock documentation.
This does not provide any of the backends, just the common interface they all use. The modules which provide the backends and their cabal packages are:
Text.Regexfrom regex-compat (uses regex-posix)
In fact, just importing one of the backends is adequate, you do not also need to import this module.
TODO: Copy Example*hs files into this haddock comment
Module that provides the Regex backend that wraps the c posix regex api. This is the backend being used by the regex-compat package to replace Text.Regex
The Text.Regex.Posix module provides a backend for regular expressions. If you import this along with other backends, then you should do so with qualified imports, perhaps renamed for convenience.
=~~ functions are too high level, you can use the
compile, regexec, and execute functions from importing either
Text.Regex.Posix.String or Text.Regex.Posix.ByteString. If you
want to use a low-level
CString interface to the library,
then import Text.Regex.Posix.Wrap and use the wrap* functions.
Note that the posix library works with single byte characters, and does not understand Unicode. If you need Unicode support you will have to use a different backend.
When offsets are reported for subexpression captures, a subexpression
that did not match anything (as opposed to matching an empty string)
will have its offset set to the
unusedRegOffset value, which is (-1).
Benchmarking shows the default regex library on many platforms is very inefficient. You might increase performace by an order of magnitude by obtaining libpcre and regex-pcre or libtre and regex-tre. If you do not need the captured substrings then you can also get great performance from regex-dfa. If you do need the capture substrings then you may be able to use regex-parsec to improve performance.
The Text.Regex.TDFA module provides a backend for regular expressions. It provides instances for the classes defined and documented in Text.Regex.Base and re-exported by this module. If you import this along with other backends then you should do so with qualified imports (with renaming for convenience).
This regex-tdfa package implements, correctly, POSIX extended regular expressions. It is highly unlikely that the regex-posix package on your operating system is correct, see http:www.haskell.orghaskellwikiRegex_Posix for examples of your OS's bugs.
This package does provide captured parenthesized subexpressions.
Depending on the text being searched this package supports Unicode. The [Char] and (Seq Char) text types support Unicode. The ByteString and ByteString.Lazy text types only support ASCII. It is possible to support utf8 encoded ByteString.Lazy by using regex-tdfa and regex-tdfa-utf8 packages together (required the utf8-string package).
As of version 1.1.1 the following GNU extensions are recognized, all anchors:
\` at beginning of entire text
\' at end of entire text
\< at beginning of word
\> at end of word
\b at either beginning or end of word
\B at neither beginning nor end of word
Where the word boundaries means between characters that are and are not in the [:word:] character class which contains [a-zA-Z0-9_]. Note that < and b may match before the entire text and > and b may match at the end of the entire text.
There is no locale support, so collating elements like [.ch.] are simply ignored and equivalence classes like [=a=] are converted to just [a]. The character classes like [:alnum:] are supported over ASCII only, valid classes are alnum, digit, punct, alpha, graph, space, blank, lower, upper, cntrl, print, xdigit, word.
This package does not provide basic regular expressions. This package does not provide back references inside regular expressions.
The package does not provide Perl style regular expressions. Please look at the regex-pcre and pcre-light packages instead.
Helper functions for defining certain instances of RegexContext. These help when defining instances of RegexContext with repeated types:
instance (RegexLike regex source) => RegexContext regex source source where
runs into overlapping restrictions. To avoid this I have each backend define, for its own Regex type:
instance RegexContext Regex String String where match = polymatch matchM = polymatchM
instance RegexContext Regex ByteString ByteString where match = polymatch matchM = polymatchM