MaybeErr(..), -- Instance of Monad
failME, isSuccess,
+ fmapM_maybe,
orElse,
mapCatMaybes,
allMaybes,
Nothing `orElse` y = y
\end{code}
+\begin{code}
+fmapM_maybe :: Monad m => (a -> m b) -> Maybe a -> m (Maybe b)
+fmapM_maybe _ Nothing = return Nothing
+fmapM_maybe f (Just x) = do
+ x' <- f x
+ return $ Just x'
+\end{code}
+
%************************************************************************
%* *
\subsection[MaybeT type]{The @MaybeT@ monad transformer}