d3c8aea · text · git.iko.soy

git.iko.soy/text

Reimplement mapAccumL properly.

--HG-- extra : convert_revision : 2a34b8e5ab564cf9025a78a27378ae75e543940d

commitd3c8aeacd0387d2642ecf7814eeb88115db2845b authorBryan O'Sullivan <bos@serpentine.com> dateSun 22 Feb 2009, 22:56 (18 years ago) parentafba704

3 files changed+15−8

compare with master

unifiedsplit

Data/Text.hs+6−6 Data/Text/Fusion.hs+8−1 tests/Properties.hs+1−1

Data/Text.hs+6−6

@@ -530,12 +530,12 @@ scanr1 f t | null t = empty

530530-- | /O(n)/ Like a combination of 'map' and 'foldl'. Applies a

531531-- function to each element of a 'Text', passing an accumulating

532532-- parameter from left to right, and returns a final 'Text'.

533−--

534−-- /Note/: Unlike the version over lists, this function does not return a

535−-- final value for the accumulator.

536−mapAccumL :: (a -> Char -> (a,Char)) -> a -> Text -> Text

537−mapAccumL f z t = unstream (S.mapAccumL f z (stream t))

538−{-# INLINE mapAccumL #-}

533+mapAccumL :: (a -> Char -> (a,Char)) -> a -> Text -> (a, Text)

534+mapAccumL f s t = case uncons t of

535+ Nothing -> (s, empty)

536+ Just (x, xs) -> (s'', cons y ys)

537+ where (s', y ) = f s x

538+ (s'',ys) = mapAccumL f s' xs

539539

540540-- -----------------------------------------------------------------------------

541541-- ** Generating and unfolding 'Text's

Data/Text/Fusion.hs+8−1

@@ -602,7 +602,14 @@ reverseScanr f z0 (Stream next0 s0 len) = Stream next (S1 :!: z0 :!: s0) (len+1)

602602-- -----------------------------------------------------------------------------

603603-- ** Accumulating maps

604604

605−mapAccumL :: (a -> Char -> (a,Char)) -> a -> Stream Char -> Stream Char

605+-- | /O(n)/ Like a combination of 'map' and 'foldl'. Applies a

606+-- function to each element of a stream, passing an accumulating

607+-- parameter from left to right, and returns a final stream.

608+--

609+-- /Note/: Unlike the version over lists, this function does not

610+-- return a final value for the accumulator, because the nature of

611+-- streams precludes it.

612+mapAccumL :: (a -> b -> (a,b)) -> a -> Stream b -> Stream b

606613mapAccumL f z0 (Stream next0 s0 len) = Stream next (s0 :!: z0) len

607614 where

608615 {-# INLINE next #-}

tests/Properties.hs+1−1

@@ -103,7 +103,7 @@ prop_scanl1 f = L.scanl1 f `eqP` (unpack . T.scanl1 f)

103103prop_scanr f z = L.scanr f z `eqP` (unpack . T.scanr f z)

104104prop_scanr1 f = L.scanr1 f `eqP` (unpack . T.scanr1 f)

105105

106−prop_mapAccumL f z = (snd . L.mapAccumL f z)`eqP` (unpack . T.mapAccumL f z)

106+prop_mapAccumL f z = L.mapAccumL f z `eqP` (second unpack . T.mapAccumL f z)

107107 where types = f :: Int -> Char -> (Int,Char)

108108

109109prop_replicate n = L.replicate n `eq` (unpack . T.replicate n)