1fde6e9 · text · git.iko.soy

Implement and test lazy scanr1

--HG-- extra : convert_revision : e8d8aaaaabd7d7fddecba64abfd1c42990abcd7f

commit1fde6e94164315aa94f4d245a92f25d43564c36f authorBryan O'Sullivan <bos@serpentine.com> dateSun 8 Mar 2009, 01:30 (18 years ago) parentddbaab6

2 files changed+9−1

unifiedsplit

Data/Text/Lazy.hs+7−1

@@ -82,7 +82,7 @@ module Data.Text.Lazy

8282 , scanl

8383 , scanl1

8484 , scanr

85− -- , scanr1

85+ , scanr1

8686

8787 -- ** Accumulating maps

8888 , mapAccumL

@@ -478,6 +478,12 @@ scanl1 f t0 = case uncons t0 of

478478scanr :: (Char -> Char -> Char) -> Char -> Text -> Text

479479scanr f v = reverse . scanl (flip f) v . reverse

480480

481+-- | /O(n)/ 'scanr1' is a variant of 'scanr' that has no starting

482+-- value argument.

483+scanr1 :: (Char -> Char -> Char) -> Text -> Text

484+scanr1 f t | null t = empty

485+ | otherwise = scanr f (last t) (init t)

486+

481487-- | /O(n)/ Like a combination of 'map' and 'foldl'. Applies a

482488-- function to each element of a 'Text', passing an accumulating

483489-- parameter from left to right, and returns a final 'Text'.

tests/Properties.hs+2

@@ -206,6 +206,7 @@ prop_TL_scanl1 f = L.scanl1 f `eqP` (unpackT . TL.scanl1 f)

206206prop_T_scanr f z = L.scanr f z `eqP` (unpackT . T.scanr f z)

207207prop_TL_scanr f z = L.scanr f z `eqP` (unpackT . TL.scanr f z)

208208prop_T_scanr1 f = L.scanr1 f `eqP` (unpackT . T.scanr1 f)

209+prop_TL_scanr1 f = L.scanr1 f `eqP` (unpackT . TL.scanr1 f)

209210

210211prop_T_mapAccumL f z = L.mapAccumL f z `eqP` (second unpackT . T.mapAccumL f z)

211212 where types = f :: Int -> Char -> (Int,Char)

@@ -435,6 +436,7 @@ tests = [

435436 ("prop_T_scanr", mytest prop_T_scanr),

436437 ("prop_TL_scanr", mytest prop_TL_scanr),

437438 ("prop_T_scanr1", mytest prop_T_scanr1),

439+ ("prop_TL_scanr1", mytest prop_TL_scanr1),

438440

439441 ("prop_T_mapAccumL", mytest prop_T_mapAccumL),

440442 ("prop_TL_mapAccumL", mytest prop_TL_mapAccumL),