35bd7d2 · text · git.iko.soy

git.iko.soy/text

Implement and test lazy drop

--HG-- extra : convert_revision : 094d6e0b44b4e56e75c0cdbf52cdd0973fefe4d0

commit35bd7d25341904362c55170ed24b6170ab662082 authorBryan O'Sullivan <bos@serpentine.com> dateTue 3 Mar 2009, 08:09 (18 years ago) parent73f9b61

3 files changed+30−3

compare with master

unifiedsplit

Data/Text/Fusion/Common.hs+3−2 Data/Text/Lazy.hs+23−1 tests/Properties.hs+4

Data/Text/Fusion/Common.hs+3−2

@@ -544,8 +544,9 @@ take n0 (Stream next0 s0 len) = Stream next (n0 :!: s0) len

544544-- | /O(n)/ drop n, applied to a stream, returns the suffix of the

545545-- stream of length @n@, or the empty stream if @n@ is greater than the

546546-- length of the stream.

547−drop :: Int -> Stream Char -> Stream Char

548−drop n0 (Stream next0 s0 len) = Stream next (Just ((max 0 n0)) :!: s0) (len - n0)

547+drop :: Integral a => a -> Stream Char -> Stream Char

548+drop n0 (Stream next0 s0 len) =

549+ Stream next (Just ((max 0 n0)) :!: s0) (len - fromIntegral n0)

549550 where

550551 {-# INLINE next #-}

551552 next (Just !n :!: s)

Data/Text/Lazy.hs+23−1

@@ -95,7 +95,7 @@ module Data.Text.Lazy

9595

9696 -- ** Breaking strings

9797 , take

98− -- , drop

98+ , drop

9999 -- , takeWhile

100100 -- , dropWhile

101101 , splitAt

@@ -514,6 +514,28 @@ take i t0 = take' i t0

514514 unstream (S.take n (stream t)) = take n t

515515 #-}

516516

517+-- | /O(n)/ 'drop' @n@, applied to a 'Text', returns the suffix of the

518+-- 'Text' of length @n@, or the empty 'Text' if @n@ is greater than the

519+-- length of the 'Text'. Subject to fusion.

520+drop :: Int -> Text -> Text

521+drop i t0

522+ | i <= 0 = t0

523+ | otherwise = drop' i t0

524+ where drop' 0 ts = ts

525+ drop' _ Empty = Empty

526+ drop' n (Chunk t ts)

527+ | n < len = Chunk (T.drop (fromIntegral n) t) ts

528+ | otherwise = drop' (n - len) ts

529+ where len = fromIntegral (T.length t)

530+{-# INLINE [1] drop #-}

531+

532+{-# RULES

533+"LAZY TEXT drop -> fused" [~1] forall n t.

534+ drop n t = unstream (S.drop n (stream t))

535+"LAZY TEXT drop -> unfused" [1] forall n t.

536+ unstream (S.drop n (stream t)) = drop n t

537+ #-}

538+

517539-- | /O(n)/ 'splitAt' @n t@ returns a pair whose first element is a

518540-- prefix of @t@ of length @n@, and whose second is the remainder of

519541-- the string. It is equivalent to @('take' n t, 'drop' n t)@.

tests/Properties.hs+4

@@ -218,7 +218,9 @@ unpack2 = unpackT *** unpackT

218218prop_S_take n = L.take n `eqP` (unpackT . S.take n)

219219prop_T_take n = L.take n `eqP` (unpackT . T.take n)

220220prop_TL_take n = L.take n `eqP` (unpackT . TL.take (fromIntegral n))

221+prop_S_drop n = L.drop n `eqP` (unpackT . S.drop n)

221222prop_T_drop n = L.drop n `eqP` (unpackT . T.drop n)

223+prop_TL_drop n = L.drop n `eqP` (unpackT . TL.drop n)

222224prop_T_takeWhile p = L.takeWhile p `eqP` (unpackT . T.takeWhile p)

223225prop_T_takeWhileS p = L.takeWhile p `eqP` (unpackT . S.unstream . S.takeWhile p . S.stream)

224226prop_T_dropWhile p = L.dropWhile p `eqP` (unpackT . T.dropWhile p)

@@ -413,7 +415,9 @@ tests = [

413415 ("prop_S_take", mytest prop_S_take),

414416 ("prop_T_take", mytest prop_T_take),

415417 ("prop_TL_take", mytest prop_TL_take),

418+ ("prop_S_drop", mytest prop_S_drop),

416419 ("prop_T_drop", mytest prop_T_drop),

420+ ("prop_TL_drop", mytest prop_TL_drop),

417421 ("prop_T_takeWhile", mytest prop_T_takeWhile),

418422 ("prop_T_takeWhileS", mytest prop_T_takeWhileS),

419423 ("prop_T_dropWhile", mytest prop_T_dropWhile),