[commit: ghc] wip/oneShot: Use oneShot in the definition of foldl etc. (6d5852a)

[git at git.haskell.org]

Repository : ssh://git@git.haskell.org/ghc

On branch  : wip/oneShot
Link       : http://ghc.haskell.org/trac/ghc/changeset/6d5852a62c4c3e4343ad5316bc0ea00a2a7a7559/ghc

>---------------------------------------------------------------

commit 6d5852a62c4c3e4343ad5316bc0ea00a2a7a7559
Author: Joachim Breitner <mail at joachim-breitner.de>
Date:   Sat Oct 25 12:27:06 2014 +0200

    Use oneShot in the definition of foldl etc.


>---------------------------------------------------------------

6d5852a62c4c3e4343ad5316bc0ea00a2a7a7559
 libraries/base/Data/OldList.hs | 5 +++--
 libraries/base/GHC/List.lhs    | 6 +++---
 2 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/libraries/base/Data/OldList.hs b/libraries/base/Data/OldList.hs
index 0e6709e..75fba35 100644
--- a/libraries/base/Data/OldList.hs
+++ b/libraries/base/Data/OldList.hs
@@ -499,7 +499,8 @@ pairWithNil x = (x, [])
 
 mapAccumLF :: (acc -> x -> (acc, y)) -> x -> (acc -> (acc, [y])) -> acc -> (acc, [y])
 {-# INLINE [0] mapAccumLF #-}
-mapAccumLF f = \x r s -> let (s', y)   = f s x
+mapAccumLF f = \x r -> oneShot $ \s -> 
+                         let (s', y)   = f s x
                              (s'', ys) = r s'
                          in (s'', y:ys)
 
@@ -1058,7 +1059,7 @@ unfoldr f b0 = build (\c n ->
 
 -- | A strict version of 'foldl'.
 foldl'           :: forall a b . (b -> a -> b) -> b -> [a] -> b
-foldl' k z0 xs = foldr (\(v::a) (fn::b->b) (z::b) -> z `seq` fn (k z v)) (id :: b -> b) xs z0
+foldl' k z0 xs = foldr (\(v::a) (fn::b->b) -> oneShot (\(z::b) -> z `seq` fn (k z v))) (id :: b -> b) xs z0
 -- Implementing foldl' via foldr is only a good idea if the compiler can optimize
 -- the resulting code (eta-expand the recursive "go"), so this needs -fcall-arity!
 -- Also see #7994
diff --git a/libraries/base/GHC/List.lhs b/libraries/base/GHC/List.lhs
index 2d01678..c7a0cb3 100644
--- a/libraries/base/GHC/List.lhs
+++ b/libraries/base/GHC/List.lhs
@@ -186,7 +186,7 @@ filterFB c p x r | p x       = x `c` r
 
 foldl :: forall a b. (b -> a -> b) -> b -> [a] -> b
 {-# INLINE foldl #-}
-foldl k z0 xs = foldr (\(v::a) (fn::b->b) (z::b) -> fn (k z v)) (id :: b -> b) xs z0
+foldl k z0 xs = foldr (\(v::a) (fn::b->b) -> oneShot (\(z::b) -> fn (k z v))) (id :: b -> b) xs z0
 -- Implementing foldl via foldr is only a good idea if the compiler can optimize
 -- the resulting code (eta-expand the recursive "go"), so this needs -fcall-arity!
 -- Also see #7994
@@ -221,7 +221,7 @@ scanl                   = scanlGo
 
 {-# INLINE [0] scanlFB #-}
 scanlFB :: (b -> a -> b) -> (b -> c -> c) -> a -> (b -> c) -> b -> c
-scanlFB f c = \b g x -> let b' = f x b in b' `c` g b'
+scanlFB f c = \b g -> oneShot (\x -> let b' = f x b in b' `c` g b')
 
 {-# INLINE [0] constScanl #-}
 constScanl :: a -> b -> a
@@ -258,7 +258,7 @@ scanl' = scanlGo'
 
 {-# INLINE [0] scanlFB' #-}
 scanlFB' :: (b -> a -> b) -> (b -> c -> c) -> a -> (b -> c) -> b -> c
-scanlFB' f c = \b g x -> let b' = f x b in b' `seq` b' `c` g b'
+scanlFB' f c = \b g -> oneShot (\x -> let b' = f x b in b' `seq` b' `c` g b')
 
 {-# INLINE [0] flipSeqScanl' #-}
 flipSeqScanl' :: a -> b -> a