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Make append stack-safe #89

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Merged
merged 1 commit into from
Dec 24, 2016
Merged

Make append stack-safe #89

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3 changes: 1 addition & 2 deletions src/Data/List/Types.purs
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Original file line number Diff line number Diff line change
Expand Up @@ -50,8 +50,7 @@ instance ordList :: Ord a => Ord (List a) where
other -> other

instance semigroupList :: Semigroup (List a) where
append Nil ys = ys
append (x : xs) ys = x : (xs <> ys)
append xs ys = foldr (:) ys xs

instance monoidList :: Monoid (List a) where
mempty = Nil
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7 changes: 7 additions & 0 deletions test/Test/Data/List.purs
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Expand Up @@ -319,6 +319,13 @@ testList = do
let xs = fromFoldable (range 1 100000)
assert $ traverse Just xs == Just xs

log "append should concatenate two lists"
assert $ (l [1, 2]) <> (l [3, 4]) == (l [1, 2, 3, 4])

log "append should be stack-safe"
void $ pure $ xs <> xs


step :: Int -> Maybe (Tuple Int Int)
step 6 = Nothing
step n = Just (Tuple n (n + 1))
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