df136e5 · typeable/attoparsec

git.iko.soy/typeable/attoparsec

Added back the lookAhead combinator

commitdf136e5be4abcf6ada9b7e8250fac5dae6072d5d authorGergely Risko <errge@nilcons.com> dateMon 23 Jun 2014, 18:41 (12 years ago) parent6791bcd

2 files changed+20−1

compare with master

unifiedsplit

Data/Attoparsec/Combinator.hs+8 tests/QC/Combinator.hs+12−1

Data/Attoparsec/Combinator.hs+8

@@ -33,6 +33,7 @@ module Data.Attoparsec.Combinator

3333 , satisfyElem

3434 , endOfInput

3535 , atEnd

36+ , lookAhead

3637 ) where

3738

3839import Control.Applicative (Alternative(..), Applicative(..), empty, liftA2,

@@ -240,3 +241,10 @@ feed f@(Fail _ _ _) _ = f

240241feed (Partial k) d = k d

241242feed (Done t r) d = Done (mappend t d) r

242243{-# INLINE feed #-}

244+

245+-- | Apply a parser without consuming any input.

246+lookAhead :: Parser i a -> Parser i a

247+lookAhead p = Parser $ \t pos more lose succ ->

248+ let succ' t' _pos' more' = succ t' pos more'

249+ in runParser p t pos more lose succ'

250+{-# INLINE lookAhead #-}

tests/QC/Combinator.hs+12−1

@@ -1,8 +1,11 @@

1+{-# LANGUAGE OverloadedStrings #-}

13module QC.Combinator where

35import Control.Applicative

6+import Data.Maybe (fromJust, isJust)

47import Data.Word (Word8)

5−import QC.Common (Repack, parseBS, repackBS)

8+import QC.Common (Repack, parseBS, repackBS, toLazyBS)

69import Test.Framework (Test)

710import Test.Framework.Providers.QuickCheck2 (testProperty)

811import Test.QuickCheck

@@ -22,6 +25,13 @@ count (Positive (Small n)) rs s =

2225 (length <$> parseBS (C.count n (P.string s)) input) == Just n

2326 where input = repackBS rs (B.concat (replicate (n+1) s))

2427

28+lookAhead :: NonEmptyList Word8 -> Bool

29+lookAhead (NonEmpty xs) =

30+ let ys = B.pack xs

31+ withLookAheadThenConsume = (\x y -> (x, y)) <$> C.lookAhead (P.string ys) <*> P.string ys

32+ mr = parseBS withLookAheadThenConsume $ toLazyBS ys

33+ in isJust mr && fst (fromJust mr) == snd (fromJust mr)

34+

2535match :: Int -> NonNegative Int -> NonNegative Int -> Repack -> Bool

2636match n (NonNegative x) (NonNegative y) rs =

2737 parseBS (P.match parser) (repackBS rs input) == Just (input, n)

@@ -35,5 +45,6 @@ tests :: [Test]

3545tests = [

3646 testProperty "choice" choice

3747 , testProperty "count" count

48+ , testProperty "lookAhead" lookAhead

3849 , testProperty "match" match

3950 ]