95b326b · text · git.iko.soy

git.iko.soy/text

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Implement and test lazy init

95b326bBryan O'Sullivan18 years ago

Data/Text/Lazy.hs+17−1

compare with master

unifiedsplit

@@ -47,7 +47,7 @@ module Data.Text.Lazy

47 , head

48 , last

49 , tail

50− -- , init

50+ , init

51 -- , null

52 -- , length

@@ -251,6 +251,8 @@ head :: Text -> Char

251head t = S.head (stream t)

252{-# INLINE head #-}

253

254+-- | /O(1)/ Returns all characters after the head of a 'Text', which

255+-- must be non-empty. Subject to array fusion.

254tail :: Text -> Text

256tail :: Text -> Text

255tail (Chunk t ts) = chunk (T.tail t) ts

257tail (Chunk t ts) = chunk (T.tail t) ts

256tail Empty = emptyError "tail"

258tail Empty = emptyError "tail"

@@ -263,6 +265,20 @@ tail Empty = emptyError "tail"

263 unstream (S.tail (stream t)) = tail t

265 unstream (S.tail (stream t)) = tail t

264 #-}

266 #-}

265

267

268+init :: Text -> Text

269+init (Chunk t0 ts0) = go t0 ts0

270+ where go t (Chunk t' ts) = Chunk t (go t' ts)

271+ go t Empty = chunk (T.init t) Empty

272+init Empty = emptyError "init"

273+{-# INLINE [1] init #-}

274+

275+{-# RULES

276+"LAZY TEXT init -> fused" [~1] forall t.

277+ init t = unstream (S.init (stream t))

278+"LAZY TEXT init -> unfused" [1] forall t.

279+ unstream (S.init (stream t)) = init t

280+ #-}

281+

266-- | /O(1)/ Returns the last character of a 'Text', which must be

282-- | /O(1)/ Returns the last character of a 'Text', which must be

267-- non-empty. Subject to array fusion.

283-- non-empty. Subject to array fusion.

268last :: Text -> Char

284last :: Text -> Char

tests/Properties.hs+4−2

@@ -130,8 +130,9 @@ prop_TL_last = last `eqEP` TL.last

130prop_S_tail = tail `eqEP` (unpackT . S.tail)

131prop_T_tail = tail `eqEP` (unpackT . T.tail)

132prop_TL_tail = tail `eqEP` (unpackT . TL.tail)

133+prop_S_init = init `eqEP` (unpackT . S.init)

133prop_T_init = init `eqEP` (unpackT . T.init)

134prop_T_init = init `eqEP` (unpackT . T.init)

134−prop_T_initS = init `eqEP` (unpackT . S.unstream . S.init . S.stream)

135+prop_TL_init = init `eqEP` (unpackT . TL.init)

135prop_T_null = null `eqP` T.null

136prop_T_null = null `eqP` T.null

136prop_T_length = length `eqP` T.length

137prop_T_length = length `eqP` T.length

137prop_T_map f = map f `eqP` (unpackT . T.map f)

138prop_T_map f = map f `eqP` (unpackT . T.map f)

@@ -308,8 +309,9 @@ tests = [

308 ("prop_S_tail", mytest prop_S_tail),

309 ("prop_S_tail", mytest prop_S_tail),

309 ("prop_T_tail", mytest prop_T_tail),

310 ("prop_T_tail", mytest prop_T_tail),

310 ("prop_TL_tail", mytest prop_TL_tail),

311 ("prop_TL_tail", mytest prop_TL_tail),

312+ ("prop_S_init", mytest prop_S_init),

311 ("prop_T_init", mytest prop_T_init),

313 ("prop_T_init", mytest prop_T_init),

312− ("prop_T_initS", mytest prop_T_initS),

314+ ("prop_TL_init", mytest prop_TL_init),

313 ("prop_T_null", mytest prop_T_null),

315 ("prop_T_null", mytest prop_T_null),

314 ("prop_T_length", mytest prop_T_length),

316 ("prop_T_length", mytest prop_T_length),

315

317