"Committed_by_peb"

src/GF/Data/Utilities.hs

@@ -0,0 +1,53 @@
+----------------------------------------------------------------------
+-- |
+-- Maintainer  : PL
+-- Stability   : (stable)
+-- Portability : (portable)
+--
+-- > CVS $Date: 2005/04/11 13:52:49 $ 
+-- > CVS $Author: peb $
+-- > CVS $Revision: 1.1 $
+--
+-- Basic functions not in the standard libraries
+-----------------------------------------------------------------------------
+
+
+module GF.Data.Utilities where
+
+-- * functions on lists
+
+sameLength :: [a] -> [a] -> Bool
+sameLength [] [] = True
+sameLength (_:xs) (_:ys) = sameLength xs ys
+sameLength _ _ = False
+
+lookupList :: Eq a => a -> [(a, b)] -> [b]
+lookupList a [] = []
+lookupList a (p:ps) | a == fst p = snd p : lookupList a ps
+		    | otherwise  =         lookupList a ps
+
+split :: [a] -> ([a], [a])
+split (x : y : as) = (x:xs, y:ys)
+    where (xs, ys) = split as
+split as = (as, [])
+
+splitBy :: (a -> Bool) -> [a] -> ([a], [a])
+splitBy p [] = ([], [])
+splitBy p (a : as) = if p a then (a:xs, ys) else (xs, a:ys)
+    where (xs, ys) = splitBy p as
+
+foldMerge :: (a -> a -> a) -> a -> [a] -> a
+foldMerge merge zero = fm
+    where fm [] = zero
+	  fm [a] = a
+	  fm abs = let (as, bs) = split abs in fm as `merge` fm bs
+
+-- * functions on pairs
+
+mapFst :: (a -> a') -> (a, b) -> (a', b)
+mapFst f (a, b) = (f a, b)
+
+mapSnd :: (b -> b') -> (a, b) -> (a, b')
+mapSnd f (a, b) = (a, f b)
+
+