regex-tdfa- Replaces/Enhances Text.Regex

Safe HaskellNone



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 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

The above are controlled by the newSyntax Bool in CompOption.

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.



(=~) :: (RegexMaker Regex CompOption ExecOption source, RegexContext Regex source1 target) => source1 -> source -> target Source #

This is the pure functional matching operator. If the target cannot be produced then some empty result will be returned. If there is an error in processing, then error will be called.

(=~~) :: (RegexMaker Regex CompOption ExecOption source, RegexContext Regex source1 target, Monad m) => source1 -> source -> m target Source #

This is the monadic matching operator. If a single match fails, then fail will be called.