Added Graphviz module for graphviz stuff. Move a lot of utility functions to GF.Data.Utilities.

src/GF/Data/Utilities.hs

@@ -4,9 +4,9 @@
 -- Stability   : (stable)
 -- Portability : (portable)
 --
--- > CVS $Date: 2005/05/09 09:28:44 $ 
--- > CVS $Author: peb $
--- > CVS $Revision: 1.2 $
+-- > CVS $Date: 2005/09/14 15:17:29 $ 
+-- > CVS $Author: bringert $
+-- > CVS $Revision: 1.3 $
 --
 -- Basic functions not in the standard libraries
 -----------------------------------------------------------------------------
@@ -14,7 +14,9 @@
 
 module GF.Data.Utilities where
 
-import Monad (liftM)
+import Data.Maybe
+import Data.List
+import Control.Monad (MonadPlus(..),liftM)
 
 -- * functions on lists
 
@@ -32,6 +34,11 @@ lookupList a [] = []
 lookupList a (p:ps) | a == fst p = snd p : lookupList a ps
 		    | otherwise  =         lookupList a ps
 
+-- | Find the first list in a list of lists
+--   which contains the argument.
+findSet :: Eq c => c -> [[c]] -> Maybe [c]
+findSet x = find (x `elem`)
+
 split :: [a] -> ([a], [a])
 split (x : y : as) = (x:xs, y:ys)
     where (xs, ys) = split as
@@ -60,6 +67,24 @@ updateNthM :: Monad m => (a -> m a) -> Int -> [a] -> m [a]
 updateNthM update 0 (a : as) = liftM (:as) (update a)
 updateNthM update n (a : as) = liftM (a:)  (updateNthM update (n-1) as)
 
+-- | Like 'init', but returns the empty list when the input is empty.
+safeInit :: [a] -> [a]
+safeInit [] = []
+safeInit xs = init xs
+
+-- | Like 'nub', but more efficient as it uses sorting internally.
+sortNub :: Ord a => [a] -> [a]
+sortNub = map head . group . sort
+
+-- | Take the union of a list of lists.
+unionAll :: Eq a => [[a]] -> [a]
+unionAll = nub . concat
+
+-- | Like lookup, but fails if the argument is not found,
+--   instead of returning Nothing.
+lookup' :: Eq a => a -> [(a,b)] -> b
+lookup' x = fromJust . lookup x
+
 -- * functions on pairs
 
 mapFst :: (a -> a') -> (a, b) -> (a', b)
@@ -68,4 +93,59 @@ mapFst f (a, b) = (f a, b)
 mapSnd :: (b -> b') -> (a, b) -> (a, b')
 mapSnd f (a, b) = (a, f b)
 
+-- * functions on monads
+
+-- | Return the given value if the boolean is true, els return 'mzero'.
+whenMP :: MonadPlus m => Bool -> a -> m a
+whenMP b x = if b then return x else mzero
+
+-- * functions on Maybes
+
+-- | Returns true if the argument is Nothing or Just []
+nothingOrNull :: Maybe [a] -> Bool
+nothingOrNull = maybe True null
+
+-- * functions on functions
+
+-- | Apply all the functions in the list to the argument.
+foldFuns :: [a -> a] -> a -> a
+foldFuns fs x = foldl (flip ($)) x fs
+
+-- | Fixpoint iteration.
+fix :: Eq a => (a -> a) -> a -> a
+fix f x = let x' = f x in if x' == x then x else fix f x'
+
+-- * functions on strings
+
+-- | Join a number of lists by using the given glue
+--   between the lists.
+join :: [a] -- ^ glue
+     -> [[a]] -- ^ lists to join
+     -> [a]
+join g = concat . intersperse g
+
+-- * ShowS-functions
+
+nl :: ShowS
+nl = showChar '\n'
+
+sp :: ShowS
+sp = showChar ' '
+
+wrap :: String -> ShowS -> String -> ShowS
+wrap o s c = showString o . s . showString c
+
+concatS :: [ShowS] -> ShowS
+concatS = foldr (.) id
+
+unwordsS :: [ShowS] -> ShowS
+unwordsS = joinS " "
+
+unlinesS :: [ShowS] -> ShowS
+unlinesS = joinS "\n"
+
+joinS :: String -> [ShowS] -> ShowS
+joinS glue = concatS . intersperse (showString glue)
+
+