044dff4 · text · git.iko.soy

git.iko.soy/text

Implement mapAccumR.

--HG-- extra : convert_revision : 845d33352bb095f1ac197c9ac75991f29f6c2b38

commit044dff47d535720ac659188f8f72b0bbfe6129e5 authorBryan O'Sullivan <bos@serpentine.com> dateSun 22 Feb 2009, 23:02 (18 years ago) parent7a617d4

2 files changed+15−1

compare with master

unifiedsplit

Data/Text.hs+12−1 tests/Properties.hs+3

Data/Text.hs+12−1

@@ -81,7 +81,7 @@ module Data.Text

8181

8282 -- ** Accumulating maps

8383 , mapAccumL

84− -- , mapAccumR

84+ , mapAccumR

8585

8686 -- ** Generation and unfolding

8787 , replicate

@@ -538,6 +538,17 @@ mapAccumL f s t = case uncons t of

538538 where (s', y ) = f s x

539539 (s'',ys) = mapAccumL f s' xs

540540

541+-- | The 'mapAccumR' function behaves like a combination of 'map' and

542+-- 'foldr'; it applies a function to each element of a 'Text', passing

543+-- an accumulating parameter from right to left, and returning a final

544+-- value of this accumulator together with the new 'Text'.

545+mapAccumR :: (a -> Char -> (a,Char)) -> a -> Text -> (a, Text)

546+mapAccumR f s t = case uncons t of

547+ Nothing -> (s, empty)

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

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

550+ (s', ys) = mapAccumR f s xs

551+

541552-- -----------------------------------------------------------------------------

542553-- ** Generating and unfolding 'Text's

543554

tests/Properties.hs+3

@@ -105,6 +105,8 @@ prop_scanr1 f = L.scanr1 f `eqP` (unpack . T.scanr1 f)

105105

106106prop_mapAccumL f z = L.mapAccumL f z `eqP` (second unpack . T.mapAccumL f z)

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

108+prop_mapAccumR f z = L.mapAccumR f z `eqP` (second unpack . T.mapAccumR f z)

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

108110

109111prop_replicate n = L.replicate n `eq` (unpack . T.replicate n)

110112prop_unfoldr n = L.unfoldr f `eq` (unpack . T.unfoldr f)

@@ -244,6 +246,7 @@ tests = [

244246 ("prop_scanr1", mytest prop_scanr1),

245247

246248 ("prop_mapAccumL", mytest prop_mapAccumL),

249+ ("prop_mapAccumR", mytest prop_mapAccumR),

247250

248251 ("prop_replicate", mytest prop_replicate),

249252 ("prop_unfoldr", mytest prop_unfoldr),