rex

A quasi-quoter for typeful results of regex captures.

http://github.com/mgsloan/rex

LTS Haskell 23.1:0.6.2
Stackage Nightly 2024-12-22:0.6.2
Latest on Hackage:0.6.2

See all snapshots rex appears in

BSD-3-Clause licensed by Michael Sloan
Maintained by Michael Sloan <mgsloan at gmail>
This version can be pinned in stack with:rex-0.6.2@sha256:5a05bb86240f911ef8d5a17c2df0e78728e57083b6d34b64e51abb747ba0e26c,1739

Module documentation for 0.6.2

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

Changelog

0.6.2

  • Now compiles with GHC-9.2. See [#14][]

0.6.1

  • Now compiles with GHC-8.10. See #13

0.6

  • Made the generated code total. See #10

0.5.1 (2014-02-20)

  • Made the type of the default ‘rexView’ fully polymorphic.

0.5: (2014-02-20)

  • 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’.

0.4.3: (2013-12-21)

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

  • Miscellaneous code cleanups.

0.4.2: (2013-02-04)

0.4: (2012-10-11)

  • Made configuration into a datatype.

0.3: (2011-09-25)

  • 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.

0.2: (2011-09-24)

  • 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.

0.1: (2011-07-25)

  • initial release