[project @ 2001-03-01 15:58:28 by simonmar]

add foldl',  a strict foldl

diff --git a/ghc/compiler/utils/Util.lhs b/ghc/compiler/utils/Util.lhs
index b351729..7cb7a3d 100644 (file)
--- a/ghc/compiler/utils/Util.lhs
+++ b/ghc/compiler/utils/Util.lhs
@@ -37,24 +37,20 @@ module Util (
        transitiveClosure,
 
        -- accumulating
-       mapAccumL, mapAccumR, mapAccumB, foldl2, count,
+       mapAccumL, mapAccumR, mapAccumB, 
+       foldl2, count,
 
        -- comparisons
        thenCmp, cmpList, prefixMatch, suffixMatch,
 
        -- strictness
-       seqList, ($!),
+       foldl', seqList,
 
        -- pairs
        IF_NOT_GHC(cfst COMMA applyToPair COMMA applyToFst COMMA)
        IF_NOT_GHC(applyToSnd COMMA foldPair COMMA)
        unzipWith
 
-       -- I/O
-#if __GLASGOW_HASKELL__ < 402
-       , bracket
-#endif
-
        , global
        , myGetProcessID
 
@@ -611,6 +607,16 @@ mapAccumB f a b (x:xs) = (a'',b'',y:ys)
        (a'',b',ys) = mapAccumB f a' b xs
 \end{code}
 
+A strict version of foldl.
+
+\begin{code}
+foldl'        :: (a -> b -> a) -> a -> [b] -> a
+foldl' f z xs = lgo z xs
+            where
+               lgo z []     =  z
+               lgo z (x:xs) = (lgo $! (f z x)) xs
+\end{code}
+
 A combination of foldl with zip.  It works with equal length lists.
 
 \begin{code}
@@ -700,29 +706,9 @@ unzipWith f pairs = map ( \ (a, b) -> f a b ) pairs
 \end{code}
 
 \begin{code}
-#if __HASKELL1__ > 4
 seqList :: [a] -> b -> b
-#else
-seqList :: (Eval a) => [a] -> b -> b
-#endif
 seqList [] b = b
 seqList (x:xs) b = x `seq` seqList xs b
-
-#if __HASKELL1__ <= 4
-($!)    :: (Eval a) => (a -> b) -> a -> b
-f $! x  = x `seq` f x
-#endif
-\end{code}
-
-\begin{code}
-#if __GLASGOW_HASKELL__ < 402
-bracket :: IO a -> (a -> IO b) -> (a -> IO c) -> IO c
-bracket before after thing = do
-  a <- before 
-  r <- (thing a) `catch` (\err -> after a >> fail err)
-  after a
-  return r
-#endif
 \end{code}
 
 Global variables: