\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 (
-- general list processing
mapFst, mapSnd,
mapAndUnzip, mapAndUnzip3,
nOfThem, filterOut, partitionWith, splitEithers,
+ foldl1',
lengthExceeds, lengthIs, lengthAtLeast,
listLengthCmp, atLength, equalLength, compareLength,
nTimes,
-- sorting
- sortLe, sortWith,
+ sortLe, sortWith, on,
-- transitive closures
transitiveClosure,
removeSpaces,
-- strictness
- foldl', seqList,
+ seqList,
-- pairs
unzipWith,
#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 )
# 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}
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}
%************************************************************************
%* *
%************************************************************************
-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}
\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