75c0703 · text · git.iko.soy

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Implement and test lazy scanl and scanl1

75c0703Bryan O'Sullivan18 years ago

Data/Text/Lazy.hs+25−2

compare with master

unifiedsplit

@@ -77,8 +77,8 @@ module Data.Text.Lazy

77 -- * Construction

79 -- ** Scans

80− -- , scanl

80+ , scanl

81− -- , scanl1

81+ , scanl1

82 -- , scanr

83 -- , scanr1

@@ -424,6 +424,29 @@ minimum :: Text -> Char

424minimum t = S.minimum (stream t)

425{-# INLINE minimum #-}

426

427+-- | /O(n)/ 'scanl' is similar to 'foldl', but returns a list of

428+-- successive reduced values from the left. This function is subject

429+-- to array fusion.

430+--

431+-- > scanl f z [x1, x2, ...] == [z, z `f` x1, (z `f` x1) `f` x2, ...]

432+--

433+-- Note that

434+--

435+-- > last (scanl f z xs) == foldl f z xs.

436+scanl :: (Char -> Char -> Char) -> Char -> Text -> Text

437+scanl f z t = unstream (S.scanl f z (stream t))

438+{-# INLINE scanl #-}

439+

440+-- | /O(n)/ 'scanl1' is a variant of 'scanl' that has no starting

441+-- value argument. This function is subject to array fusion.

442+--

443+-- > scanl1 f [x1, x2, ...] == [x1, x1 `f` x2, ...]

444+scanl1 :: (Char -> Char -> Char) -> Text -> Text

445+scanl1 f t0 = case uncons t0 of

446+ Nothing -> empty

447+ Just (t,ts) -> scanl f t ts

448+{-# INLINE scanl1 #-}

449+

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

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

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

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

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

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

tests/Properties.hs+4

@@ -183,7 +183,9 @@ prop_T_minimum = L.minimum `eqEP` T.minimum

183prop_TL_minimum = L.minimum `eqEP` TL.minimum

184

185prop_T_scanl f z = L.scanl f z `eqP` (unpackT . T.scanl f z)

186+prop_TL_scanl f z = L.scanl f z `eqP` (unpackT . TL.scanl f z)

186prop_T_scanl1 f = L.scanl1 f `eqP` (unpackT . T.scanl1 f)

187prop_T_scanl1 f = L.scanl1 f `eqP` (unpackT . T.scanl1 f)

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

187prop_T_scanr f z = L.scanr f z `eqP` (unpackT . T.scanr f z)

189prop_T_scanr f z = L.scanr f z `eqP` (unpackT . T.scanr f z)

188prop_T_scanr1 f = L.scanr1 f `eqP` (unpackT . T.scanr1 f)

190prop_T_scanr1 f = L.scanr1 f `eqP` (unpackT . T.scanr1 f)

189

191

@@ -380,7 +382,9 @@ tests = [

380 ("prop_TL_minimum", mytest prop_TL_minimum),

382 ("prop_TL_minimum", mytest prop_TL_minimum),

381

383

382 ("prop_T_scanl", mytest prop_T_scanl),

384 ("prop_T_scanl", mytest prop_T_scanl),

385+ ("prop_TL_scanl", mytest prop_TL_scanl),

383 ("prop_T_scanl1", mytest prop_T_scanl1),

386 ("prop_T_scanl1", mytest prop_T_scanl1),

387+ ("prop_TL_scanl1", mytest prop_TL_scanl1),

384 ("prop_T_scanr", mytest prop_T_scanr),

388 ("prop_T_scanr", mytest prop_T_scanr),

385 ("prop_T_scanr1", mytest prop_T_scanr1),

389 ("prop_T_scanr1", mytest prop_T_scanr1),

386

390