1a7653a · text · git.iko.soy

git.iko.soy/text

Implement and test lazy scanr and reverse

--HG-- extra : convert_revision : af450f27ecc5d40ed62e1d944aaeee4bbda71f9d

commit1a7653a64119e40ae678f7dd626285851fe5461f authorBryan O'Sullivan <bos@serpentine.com> dateSun 8 Mar 2009, 01:26 (18 years ago) parentf2565d2

3 files changed+19−3

compare with master

unifiedsplit

Data/Text.hs+1−1 Data/Text/Lazy.hs+14−2 tests/Properties.hs+4

Data/Text.hs+1−1

@@ -500,7 +500,7 @@ scanl1 f t | null t = empty

500500

501501-- | /O(n)/ 'scanr' is the right-to-left dual of 'scanl'.

502502--

503−-- > scanr f v t == reverse (scanl (flip f) v t)

503+-- > scanr f v == reverse . scanl (flip f) v . reverse

504504scanr :: (Char -> Char -> Char) -> Char -> Text -> Text

505505scanr f z = S.reverse . S.reverseScanr f z . reverseStream

506506{-# INLINE scanr #-}

Data/Text/Lazy.hs+14−2

@@ -58,7 +58,7 @@ module Data.Text.Lazy

5858 , intercalate

5959 , intersperse

6060 , transpose

61− -- , reverse

61+ , reverse

6262

6363 -- * Folds

6464 , foldl

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

8181 -- ** Scans

8282 , scanl

8383 , scanl1

84− -- , scanr

84+ , scanr

8585 -- , scanr1

8686

8787 -- ** Accumulating maps

@@ -363,6 +363,12 @@ transpose ts = L.map (\ss -> Chunk (T.pack ss) Empty)

363363 (L.transpose (L.map unpack ts))

364364-- TODO: make this fast

365365

366+-- | /O(n)/ 'reverse' @t@ returns the elements of @t@ in reverse order.

367+reverse :: Text -> Text

368+reverse = rev Empty

369+ where rev a Empty = a

370+ rev a (Chunk t ts) = rev (Chunk (T.reverse t) a) ts

371+

366372-- | /O(n)/ 'foldl', applied to a binary operator, a starting value

367373-- (typically the left-identity of the operator), and a 'Text',

368374-- reduces the 'Text' using the binary operator, from left to right.

@@ -466,6 +472,12 @@ scanl1 f t0 = case uncons t0 of

466472 Just (t,ts) -> scanl f t ts

467473{-# INLINE scanl1 #-}

468474

475+-- | /O(n)/ 'scanr' is the right-to-left dual of 'scanl'.

476+--

477+-- > scanr f v == reverse . scanl (flip f) v . reverse

478+scanr :: (Char -> Char -> Char) -> Char -> Text -> Text

479+scanr f v = reverse . scanl (flip f) v . reverse

480+

469481-- | /O(n)/ Like a combination of 'map' and 'foldl'. Applies a

470482-- function to each element of a 'Text', passing an accumulating

471483-- parameter from left to right, and returns a final 'Text'.

tests/Properties.hs+4

@@ -159,6 +159,7 @@ prop_TL_intersperse c = L.intersperse c `eqP` (unpackT . TL.intersperse c)

159159prop_T_transpose = L.transpose `eq` (map unpackT . T.transpose . map T.pack)

160160prop_TL_transpose = L.transpose `eq` (map unpackT . TL.transpose . map TL.pack)

161161prop_T_reverse = L.reverse `eqP` (unpackT . T.reverse)

162+prop_TL_reverse = L.reverse `eqP` (unpackT . TL.reverse)

162163prop_T_reverse_short n = L.reverse `eqP` (unpackT . S.reverse . shorten n . S.stream)

163164

164165prop_T_foldl f z = L.foldl f z `eqP` (T.foldl f z)

@@ -198,6 +199,7 @@ prop_TL_scanl f z = L.scanl f z `eqP` (unpackT . TL.scanl f z)

198199prop_T_scanl1 f = L.scanl1 f `eqP` (unpackT . T.scanl1 f)

199200prop_TL_scanl1 f = L.scanl1 f `eqP` (unpackT . TL.scanl1 f)

200201prop_T_scanr f z = L.scanr f z `eqP` (unpackT . T.scanr f z)

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

201203prop_T_scanr1 f = L.scanr1 f `eqP` (unpackT . T.scanr1 f)

202204

203205prop_T_mapAccumL f z = L.mapAccumL f z `eqP` (second unpackT . T.mapAccumL f z)

@@ -392,6 +394,7 @@ tests = [

392394 ("prop_T_transpose", mytest prop_T_transpose),

393395 ("prop_TL_transpose", mytest prop_TL_transpose),

394396 ("prop_T_reverse", mytest prop_T_reverse),

397+ ("prop_TL_reverse", mytest prop_TL_reverse),

395398 ("prop_T_reverse_short", mytest prop_T_reverse_short),

396399

397400 ("prop_T_foldl", mytest prop_T_foldl),

@@ -425,6 +428,7 @@ tests = [

425428 ("prop_T_scanl1", mytest prop_T_scanl1),

426429 ("prop_TL_scanl1", mytest prop_TL_scanl1),

427430 ("prop_T_scanr", mytest prop_T_scanr),

431+ ("prop_TL_scanr", mytest prop_TL_scanr),

428432 ("prop_T_scanr1", mytest prop_T_scanr1),

429433

430434 ("prop_T_mapAccumL", mytest prop_T_mapAccumL),