Fix the build with GHC < 6.4 (foldl1' didn't exist)

[ghc-hetmet.git] / compiler / utils / Util.lhs

diff --git a/compiler/utils/Util.lhs b/compiler/utils/Util.lhs
index 8473faf..eb8595d 100644 (file)
--- a/compiler/utils/Util.lhs
+++ b/compiler/utils/Util.lhs
@@ -5,14 +5,24 @@
 \section[Util]{Highly random utility functions}
 
 \begin{code}
+{-# OPTIONS -w #-}
+-- The above warning supression flag is a temporary kludge.
+-- While working on this module you are encouraged to remove it and fix
+-- any warnings in the module. See
+--     http://hackage.haskell.org/trac/ghc/wiki/Commentary/CodingStyle#Warnings
+-- for details
+
 module Util (
 
+    foldl1',
+
        -- general list processing
        zipEqual, zipWithEqual, zipWith3Equal, zipWith4Equal,
         zipLazy, stretchZipWith,
        mapFst, mapSnd,
        mapAndUnzip, mapAndUnzip3,
        nOfThem, filterOut, partitionWith, splitEithers,
+        foldl1',
 
        lengthExceeds, lengthIs, lengthAtLeast, 
        listLengthCmp, atLength, equalLength, compareLength,
@@ -26,7 +36,7 @@ module Util (
        nTimes,
 
        -- sorting
-       sortLe, sortWith,
+       sortLe, sortWith, on,
 
        -- transitive closures
        transitiveClosure,
@@ -79,20 +89,23 @@ module Util (
 
 #include "HsVersions.h"
 
-import Panic           ( panic, trace )
 import FastTypes
 
+#if defined(DEBUG) || __GLASGOW_HASKELL__ < 604
+import Panic
+#endif
+
 import Control.Exception ( Exception(..), finally, catchDyn, throw )
 import qualified Control.Exception as Exception
 import Data.Dynamic    ( Typeable )
 import Data.IORef      ( IORef, newIORef )
 import System.IO.Unsafe        ( unsafePerformIO )
 import Data.IORef      ( readIORef, writeIORef )
+import Data.List        hiding (group)
 
-import qualified Data.List as List ( elem, notElem )
-
-#ifndef DEBUG
-import Data.List               ( zipWith4 )
+import qualified Data.List as List ( elem )
+#ifdef DEBUG
+import qualified Data.List as List ( notElem )
 #endif
 
 import Control.Monad   ( when )
@@ -106,6 +119,15 @@ import System.Time ( ClockTime )
 infixr 9 `thenCmp`
 \end{code}
 
+\begin{code}
+#if __GLASGOW_HASKELL__ < 603
+-- foldl1' was introduce in GHC 6.4
+foldl1'                  :: (a -> a -> a) -> [a] -> a
+foldl1' f (x:xs)         =  foldl' f x xs
+foldl1' _ []             =  errorEmptyList "foldl1'"
+#endif
+\end{code}
+
 %************************************************************************
 %*                                                                     *
 \subsection{A for loop}
@@ -352,6 +374,16 @@ isn'tIn msg x ys
 # endif /* DEBUG */
 \end{code}
 
+foldl1' was added in GHC 6.4
+
+\begin{code}
+#if __GLASGOW_HASKELL__ < 604
+foldl1'                  :: (a -> a -> a) -> [a] -> a
+foldl1' f (x:xs)         =  foldl' f x xs
+foldl1' _ []             =  panic "foldl1'"
+#endif
+\end{code}
+
 %************************************************************************
 %*                                                                     *
 \subsubsection[Utils-Carsten-mergesort]{A mergesort from Carsten}
@@ -453,6 +485,10 @@ sortWith :: Ord b => (a->b) -> [a] -> [a]
 sortWith get_key xs = sortLe le xs
   where
     x `le` y = get_key x < get_key y   
+
+on :: (a -> a -> Ordering) -> (b -> a) -> b -> b -> Ordering
+on cmp sel = \x y -> sel x `cmp` sel y
+
 \end{code}
 
 %************************************************************************
@@ -586,6 +622,8 @@ cmpList cmp (a:as) (b:bs)
 \end{code}
 
 \begin{code}
+-- This (with a more general type) is Data.List.stripPrefix from GHC 6.8.
+-- This definition can be removed once we require at least 6.8 to build.
 maybePrefixMatch :: String -> String -> Maybe String
 maybePrefixMatch []    rest = Just rest
 maybePrefixMatch (_:_) []   = Nothing