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" == 213.33333333333334peano :: String -> Maybe Int
peano = [rex|^(?{ length . filter (=='S') } \s* (?:S\s+)*Z)\s*$|]
-- peano "S Z" == Just 1
-- peano "S S S S Z" == Just 4
-- peano "S S Z" == Just 2parsePair :: String -> Maybe (String, String)
parsePair = [rex|^<\s* (?{ }[^\s,>]+) \s*,\s* (?{ }[^\s,>]+) \s*>$|]
-- 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'