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Write custom foldl' and foldr' methods #113

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86 changes: 80 additions & 6 deletions Data/Sequence.hs
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Original file line number Diff line number Diff line change
Expand Up @@ -169,10 +169,7 @@ import Control.DeepSeq (NFData(rnf))
import Control.Monad (MonadPlus(..), ap)
import Data.Monoid (Monoid(..))
import Data.Functor (Functor(..))
import Data.Foldable (Foldable(foldl, foldl1, foldr, foldr1, foldMap), foldl', toList)
#if MIN_VERSION_base(4,8,0)
import Data.Foldable (foldr')
#endif
import Data.Foldable (Foldable(foldl, foldl1, foldr, foldr1, foldMap), foldl', foldr', toList)
import Data.Traversable
import Data.Typeable

Expand Down Expand Up @@ -241,14 +238,41 @@ fmapSeq f (Seq xs) = Seq (fmap (fmap f) xs)

instance Foldable Seq where
foldMap f (Seq xs) = foldMap (foldMap f) xs
foldr f z (Seq xs) = foldr (flip (foldr f)) z xs
foldr f z (Seq xs) = foldr f' z xs
#if __GLASGOW_HASKELL__ >= 708
where f' = coerce f
#else
where f' = flip (foldr f)
#endif

foldl f z (Seq xs) = foldl (foldl f) z xs


#if MIN_VERSION_base(4,6,0)
foldr' f z (Seq xs) = foldr' f' z xs
#if __GLASGOW_HASKELL__ >= 708
where f' = coerce f
#else
where f' = flip (foldr' f)
#endif

foldl' f z (Seq xs) = foldl' (foldl' f) z xs
#endif


foldr1 f (Seq xs) = getElem (foldr1 f' xs)
#if __GLASGOW_HASKELL__ >= 708
where f' = coerce f
#else
where f' (Elem x) (Elem y) = Elem (f x y)
#endif

foldl1 f (Seq xs) = getElem (foldl1 f' xs)
#if __GLASGOW_HASKELL__ >= 708
where f' = coerce f
#else
where f' (Elem x) (Elem y) = Elem (f x y)
#endif

#if MIN_VERSION_base(4,8,0)
length = length
Expand Down Expand Up @@ -619,11 +643,25 @@ instance Foldable FingerTree where
foldr f z (Deep _ pr m sf) =
foldr f (foldr (flip (foldr f)) (foldr f z sf) m) pr

#if MIN_VERSION_base(4,6,0)
foldr' _ z Empty = z
foldr' f z (Single x) = x `f` z
foldr' f z (Deep _ pr m sf) =
(foldr' f $! (foldr' (flip (foldr' f)) $! (foldr' f z sf)) m) pr
#endif

foldl _ z Empty = z
foldl f z (Single x) = z `f` x
foldl f z (Deep _ pr m sf) =
foldl f (foldl (foldl f) (foldl f z pr) m) sf

#if MIN_VERSION_base(4,6,0)
foldl' _ z Empty = z
foldl' f z (Single x) = z `f` x
foldl' f z (Deep _ pr m sf) =
(foldl' f $! ((foldl' (foldl' f) $! (foldl' f z pr)) m)) sf
#endif

foldr1 _ Empty = error "foldr1: empty sequence"
foldr1 _ (Single x) = x
foldr1 f (Deep _ pr m sf) =
Expand Down Expand Up @@ -702,11 +740,25 @@ instance Foldable Digit where
foldr f z (Three a b c) = a `f` (b `f` (c `f` z))
foldr f z (Four a b c d) = a `f` (b `f` (c `f` (d `f` z)))

#if MIN_VERSION_base(4,6,0)
foldr' f z (One a) = f a z
foldr' f z (Two a b) = f a $! f b z
foldr' f z (Three a b c) = f a $! f b $! f c z
foldr' f z (Four a b c d) = f a $! f b $! f c $! f d z
#endif

foldl f z (One a) = z `f` a
foldl f z (Two a b) = (z `f` a) `f` b
foldl f z (Three a b c) = ((z `f` a) `f` b) `f` c
foldl f z (Four a b c d) = (((z `f` a) `f` b) `f` c) `f` d

#if MIN_VERSION_base(4,6,0)
foldl' f z (One a) = f z a
foldl' f z (Two a b) = (f $! f z a) b
foldl' f z (Three a b c) = (f $! (f $! f z a) b) c
foldl' f z (Four a b c d) = (f $! (f $! (f $! f z a) b) c) d
#endif

foldr1 _ (One a) = a
foldr1 f (Two a b) = a `f` b
foldr1 f (Three a b c) = a `f` (b `f` c)
Expand Down Expand Up @@ -773,9 +825,19 @@ instance Foldable Node where
foldr f z (Node2 _ a b) = a `f` (b `f` z)
foldr f z (Node3 _ a b c) = a `f` (b `f` (c `f` z))

#if MIN_VERSION_base(4,6,0)
foldr' f z (Node2 _ a b) = f a $! f b z
foldr' f z (Node3 _ a b c) = f a $! f b $! f c z
#endif

foldl f z (Node2 _ a b) = (z `f` a) `f` b
foldl f z (Node3 _ a b c) = ((z `f` a) `f` b) `f` c

#if MIN_VERSION_base(4,6,0)
foldl' f z (Node2 _ a b) = (f $! f z a) b
foldl' f z (Node3 _ a b c) = (f $! (f $! f z a) b) c
#endif

instance Functor Node where
{-# INLINE fmap #-}
fmap f (Node2 v a b) = Node2 v (f a) (f b)
Expand Down Expand Up @@ -825,9 +887,21 @@ instance Functor Elem where
#endif

instance Foldable Elem where
#if __GLASGOW_HASKELL__ >= 708
foldMap = coerce
foldl = coerce
foldl' = coerce
#else
foldMap f (Elem x) = f x
foldr f z (Elem x) = f x z
foldl f z (Elem x) = f z x
#if MIN_VERSION_base(4,6,0)
foldl' f z (Elem x) = f z x
#endif
#endif
foldr f z (Elem x) = f x z
#if MIN_VERSION_base(4,6,0)
foldr' f z (Elem x) = f x z
#endif

instance Traversable Elem where
traverse f (Elem x) = Elem <$> f x
Expand Down