rex

A quasi-quoter for typeful results of regex captures. http://github.com/mgsloan/rex

Latest on Hackage:0.5.2

This package is not currently in any snapshots. If you're interested in using it, we recommend adding it to Stackage Nightly. Doing so will make builds more reliable, and allow stackage.org to host generated Haddocks.

BSD3 licensed by Michael Sloan
Maintained by Michael Sloan <mgsloan at gmail>

http://hackage.haskell.org/package/rex

Provides a quasi-quoter for regular expressions which yields a tuple, of appropriate arity and types, representing the results of the captures. Allows the user to specify parsers for captures as inline Haskell. Can also be used to provide typeful pattern matching in function definitions and case patterns.

To build / install:

./Setup.hs configure --user
./Setup.hs build
./Setup.hs install

See the haddock or Text/Regex/PCRE/Rex.hs for documentation.

Some examples (verbatim from Test.hs):

math x = mathl x 0

mathl [] x = x
mathl [rex|^  \s*(?{ read -> y }\d+)\s*(?{ s }.*)$|] x = mathl s y
mathl [rex|^\+\s*(?{ read -> y }\d+)\s*(?{ s }.*)$|] x = mathl s $ x + y
mathl [rex|^ -\s*(?{ read -> y }\d+)\s*(?{ s }.*)$|] x = mathl s $ x - y
mathl [rex|^\*\s*(?{ read -> y }\d+)\s*(?{ s }.*)$|] x = mathl s $ x * y
mathl [rex|^ /\s*(?{ read -> y }\d+)\s*(?{ s }.*)$|] x = mathl s $ x / y
mathl str x = error str

-- math "1 + 3" == 4.0
-- math "3 * 2 + 100" == 106.0
-- math "20 / 3 + 100 * 2" == 213.33333333333334
peano :: String -> Maybe Int
peano = [rex|^(?{ length . filter (=='S') } \s* (?:S\s+)*Z)\s*$|]

--  peano "S Z" == Just 1
--  peano "S S S S Z" == Just 4
--  peano "S   S   Z" == Just 2
parsePair :: String -> Maybe (String, String)
parsePair = [rex|^<\s* (?{ }[^\s,>]+) \s*,\s* (?{ }[^\s,>]+) \s*>$|]

--  parsePair "<-1, 3>" == Just ("-1","3")
--  parsePair "<-4,3b0>" == Just ("-4","3b0")
--  parsePair "< a,  -30 >" == Just ("a","-30")
--  parsePair "< a,  other>" == Just ("a","other")
-- From http://www.regular-expressions.info/dates.html
parseDate :: String -> Maybe (Int, Int, Int)
parseDate [rex|^(?{ read -> y }(?:19|20)\d\d)[- /.]
                (?{ read -> m }0[1-9]|1[012])[- /.]
                (?{ read -> d }0[1-9]|[12][0-9]|3[01])$|]
  |  (d > 30 && (m `elem` [4, 6, 9, 11]))
  || (m == 2 &&
       (d ==29 && not (mod y 4 == 0 && (mod y 100 /= 0 || mod y 400 == 0)))
    || (d > 29)) = Nothing
  | otherwise = Just (y, m, d)
parseDate _ = Nothing

--  parseDate "1993.8.10" == Nothing
--  parseDate "1993.08.10" == Just (1993,8,10)
--  parseDate "2003.02.28" == Just (2003,2,28)
--  parseDate "2003.02.27" == Just (2003,2,27)
onNull a f [] = a
onNull _ f xs = f xs

nonNull = onNull Nothing

disjunct [rex| ^(?:(?{nonNull $ Just . head -> a} .)
             | (?{nonNull $ Just . head -> b} ..)
             | (?{nonNull $ Just . last -> c} ...))$|] =
  head $ catMaybes [a, b, c]

--  disjunct "a" == 'a'
--  disjunct "ab" == 'a'
--  disjunct "abc" == 'c'

Changes

0.1: Jul 25 2011

  • initial release

0.2: Sep 24 2011

  • Added custom configuration of PCRE options.
  • Added non-precompiling quasiquoters.
  • Fixed a bug where patterns with no captures would fail.
  • Decided to remove the defaulting to 'read' - too much magic.

0.3: Sep 25 2011 Fixed a capture indexing bug, where capture fields which aren't bound would cause subsequent bound captures to be incorrect. Above bug fix actually neatened up code. * Added configuration of default mapping pattern.

0.4: Oct 11 2012

  • Made configuration into a datatype.

0.4.2: Feb 4 2013

0.4.3: Dec 21 2013

  • Patch from aavogt! to use haskell-src-exts to parse view patterns.
  • Miscellaneous code cleanups.

0.5: Feb 20 2014

  • Changed the configuration datatype to allow custom preprocessing of expr / pat antiquotes. The default match processing is now "rexView", an identifier that can be shadowed locally or hidden on import.
  • Removed 'maybeRead'.

0.5.1: Feb 20 2014

  • Made the type of the default 'rexView' fully polymorphic.
comments powered byDisqus