Remove uses of Data.Traversable to fix stage1 on pre ghc-6.6 systems

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

diff --git a/compiler/utils/Maybes.lhs b/compiler/utils/Maybes.lhs
index 7d1fa4e..af7d3f6 100644 (file)
--- a/compiler/utils/Maybes.lhs
+++ b/compiler/utils/Maybes.lhs
@@ -17,7 +17,7 @@ module Maybes (
        expectJust,
        maybeToBool,
 
-       thenMaybe, seqMaybe, returnMaybe, failMaybe
+       thenMaybe, seqMaybe, returnMaybe, failMaybe, fmapMMaybe
     ) where
 
 #include "HsVersions.h"
@@ -100,6 +100,11 @@ failMaybe = Nothing
 orElse :: Maybe a -> a -> a
 (Just x) `orElse` y = x
 Nothing  `orElse` y = y
+
+fmapMMaybe :: Monad m => (a -> m b) -> Maybe a -> m (Maybe b)
+fmapMMaybe f Nothing  = return Nothing
+fmapMMaybe f (Just x) = f x >>= \x' -> return (Just x')
+
 \end{code}