[project @ 1996-12-19 18:35:23 by simonpj]

[ghc-hetmet.git] / ghc / lib / required / Maybe.lhs

diff --git a/ghc/lib/required/Maybe.hs b/ghc/lib/required/Maybe.lhs
similarity index 72%
rename from ghc/lib/required/Maybe.hs
rename to ghc/lib/required/Maybe.lhs
index aa51ba1..7655a49 100644 (file)
--- a/ghc/lib/required/Maybe.hs
+++ b/ghc/lib/required/Maybe.lhs
@@ -1,6 +1,34 @@
+%
+% (c) The AQUA Project, Glasgow University, 1994-1996
+%
+
+\section[Maybe]{Module @Maybe@}
+
+\begin{code}
 module Maybe(
+    Maybe(..),
     the, exists, theExists, maybe, fromMaybe, listToMaybe, maybeToList,
-    findMaybe, catMaybes, mapMaybe, joinMaybe, unfoldr ) where
+    findMaybe, catMaybes, mapMaybe, joinMaybe, unfoldr
+  ) where
+
+import Prelude ()
+import IOBase  ( error )
+import Monad   ( filter )
+import PrelList
+import PrelBase
+\end{code}
+
+
+%*********************************************************
+%*                                                     *
+\subsection{Functions}
+%*                                                     *
+%*********************************************************
+
+\begin{code}
+maybe                   :: b -> (a -> b) -> Maybe a -> b
+maybe n f Nothing       =  n
+maybe n f (Just x)      =  f x
 
 exists                 :: Maybe a -> Bool
 exists                 =  maybe False (const True)
@@ -50,3 +78,4 @@ unfoldr f x =
   case f x of
   Just (y,x') -> let (ys,x'') = unfoldr f x' in (y:ys,x'')
   Nothing     -> ([],x)
+\end{code}