[project @ 2005-04-04 11:55:11 by simonpj]

[ghc-hetmet.git] / ghc / compiler / utils / IOEnv.hs

diff --git a/ghc/compiler/utils/IOEnv.hs b/ghc/compiler/utils/IOEnv.hs
index 847a46e..c217c19 100644 (file)
--- a/ghc/compiler/utils/IOEnv.hs
+++ b/ghc/compiler/utils/IOEnv.hs
@@ -8,7 +8,7 @@ module IOEnv (
 
        -- Standard combinators, specialised
        returnM, thenM, thenM_, failM,
-       mappM, mappM_, sequenceM, foldlM, 
+       mappM, mappM_, mapSndM, sequenceM, foldlM, 
        mapAndUnzipM, mapAndUnzip3M, 
        checkM, ifM, zipWithM, zipWithM_,
 
@@ -148,6 +148,7 @@ updEnv upd (IOEnv m) = IOEnv (\ env -> m (upd env))
 
 mappM                :: (a -> IOEnv env b) -> [a] -> IOEnv env [b]
 mappM_               :: (a -> IOEnv env b) -> [a] -> IOEnv env ()
+mapSndM       :: (b -> IOEnv env c) -> [(a,b)] -> IOEnv env [(a,c)]
        -- Funny names to avoid clash with Prelude
 sequenceM     :: [IOEnv env a] -> IOEnv env [a]
 foldlM        :: (a -> b -> IOEnv env a)  -> a -> [b] -> IOEnv env a
@@ -159,6 +160,9 @@ ifM       :: Bool -> IOEnv env () -> IOEnv env ()   -- Perform arg if bool is True
 mappM f []     = return []
 mappM f (x:xs) = do { r <- f x; rs <- mappM f xs; return (r:rs) }
 
+mapSndM f []     = return []
+mapSndM f ((a,b):xs) = do { c <- f b; rs <- mapSndM f xs; return ((a,c):rs) }
+
 mappM_ f []     = return ()
 mappM_ f (x:xs) = f x >> mappM_ f xs