7534f3c · text · git.iko.soy

git.iko.soy/text

Implement takeWhileEnd

This commit adds a takeWhileEnd function to both Data.Text and Data.Text.Lazy, and related QuickCheck properties. takeWhileEnd, applied to a predicate `p' and a Text `t', returns the longest suffix (possibly empty) of elements in `t' that satisfy `p'.

commit7534f3cc81461468d74c587cb36cf5a2ed5d2a19 authorPaul Capron <paul@fragara.com> dateThu 8 Oct 2015, 00:18 (11 years ago) parent93e3705

3 files changed+43

compare with master

unifiedsplit

Data/Text.hs+22 Data/Text/Lazy.hs+15 tests/Tests/Properties.hs+6

Data/Text.hs+22

@@ -129,6 +129,7 @@ module Data.Text

129129 , drop

130130 , dropEnd

131131 , takeWhile

132+ , takeWhileEnd

132133 , dropWhile

133134 , dropWhileEnd

134135 , dropAround

@@ -1124,6 +1125,27 @@ takeWhile p t@(Text arr off len) = loop 0

11241125 unstream (S.takeWhile p (stream t)) = takeWhile p t

11251126 #-}

11261127

1128+-- | /O(n)/ 'takeWhileEnd', applied to a predicate @p@ and a 'Text',

1129+-- returns the longest suffix (possibly empty) of elements that

1130+-- satisfy @p@. Subject to fusion.

1131+-- Examples:

1132+--

1133+-- > takeWhileEnd (=='o') "foo" == "oo"

1134+takeWhileEnd :: (Char -> Bool) -> Text -> Text

1135+takeWhileEnd p t@(Text arr off len) = loop (len-1) len

1136+ where loop !i !l | l <= 0 = t

1137+ | p c = loop (i+d) (l+d)

1138+ | otherwise = text arr (off+l) (len-l)

1139+ where (c,d) = reverseIter t i

1140+{-# INLINE [1] takeWhileEnd #-}

1141+

1142+{-# RULES

1143+"TEXT takeWhileEnd -> fused" [~1] forall p t.

1144+ takeWhileEnd p t = S.reverse (S.takeWhile p (S.reverseStream t))

1145+"TEXT takeWhileEnd -> unfused" [1] forall p t.

1146+ S.reverse (S.takeWhile p (S.reverseStream t)) = takeWhileEnd p t

1147+ #-}

1148+

11271149-- | /O(n)/ 'dropWhile' @p@ @t@ returns the suffix remaining after

11281150-- 'takeWhile' @p@ @t@. Subject to fusion.

11291151dropWhile :: (Char -> Bool) -> Text -> Text

Data/Text/Lazy.hs+15

@@ -140,6 +140,7 @@ module Data.Text.Lazy

140140 , drop

141141 , dropEnd

142142 , takeWhile

143+ , takeWhileEnd

143144 , dropWhile

144145 , dropWhileEnd

145146 , dropAround

@@ -1119,6 +1120,20 @@ takeWhile p t0 = takeWhile' t0

11191120"LAZY TEXT takeWhile -> unfused" [1] forall p t.

11201121 unstream (S.takeWhile p (stream t)) = takeWhile p t

11211122 #-}

1123+-- | /O(n)/ 'takeWhileEnd', applied to a predicate @p@ and a 'Text',

1124+-- returns the longest suffix (possibly empty) of elements that

1125+-- satisfy @p@.

1126+-- Examples:

1127+--

1128+-- > takeWhileEnd (=='o') "foo" == "oo"

1129+takeWhileEnd :: (Char -> Bool) -> Text -> Text

1130+takeWhileEnd p = takeChunk empty . L.reverse . toChunks

1131+ where takeChunk acc [] = acc

1132+ takeChunk acc (t:ts) = if T.length t' < T.length t

1133+ then (Chunk t' acc)

1134+ else takeChunk (Chunk t' acc) ts

1135+ where t' = T.takeWhileEnd p t

1136+{-# INLINE takeWhileEnd #-}

11221137

11231138-- | /O(n)/ 'dropWhile' @p@ @t@ returns the suffix remaining after

11241139-- 'takeWhile' @p@ @t@. Subject to fusion.

tests/Tests/Properties.hs+6

@@ -516,6 +516,10 @@ sf_takeWhile q p = (L.takeWhile p . L.filter q) `eqP`

516516 (unpackS . S.takeWhile p . S.filter q)

517517t_takeWhile p = L.takeWhile p `eqP` (unpackS . T.takeWhile p)

518518tl_takeWhile p = L.takeWhile p `eqP` (unpackS . TL.takeWhile p)

519+t_takeWhileEnd p = (L.reverse . L.takeWhile p . L.reverse) `eqP`

520+ (unpackS . T.takeWhileEnd p)

521+tl_takeWhileEnd p = (L.reverse . L.takeWhile p . L.reverse) `eqP`

522+ (unpackS . TL.takeWhileEnd p)

519523s_dropWhile p = L.dropWhile p `eqP` (unpackS . S.dropWhile p)

520524s_dropWhile_s p = L.dropWhile p `eqP` (unpackS . S.unstream . S.dropWhile p)

521525sf_dropWhile q p = (L.dropWhile p . L.filter q) `eqP`

@@ -1142,6 +1146,8 @@ tests =

11421146 testProperty "sf_takeWhile" sf_takeWhile,

11431147 testProperty "t_takeWhile" t_takeWhile,

11441148 testProperty "tl_takeWhile" tl_takeWhile,

1149+ testProperty "t_takeWhileEnd" t_takeWhileEnd,

1150+ testProperty "tl_takeWhileEnd" tl_takeWhileEnd,

11451151 testProperty "sf_dropWhile" sf_dropWhile,

11461152 testProperty "s_dropWhile" s_dropWhile,

11471153 testProperty "s_dropWhile_s" s_dropWhile_s,