A Haskell quasi-quoter for typeful results of regex captures.
Haskell
Fetching latest commit…
Cannot retrieve the latest commit at this time.
Failed to load latest commit information.
Text/Regex/PCRE
.gitignore
.travis.yml
Bench.hs
CHANGES.md
Demo.hs
LICENSE
README.md
Setup.hs
rex.cabal

README.md

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'