X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Futils%2FMaybes.lhs;h=6dd9251e66ce17106bbcab40cecfece725572814;hb=8ddfc3c10a9d08e11812b5564da291d7024d5fc8;hp=98efdb7fa13446a439185766d7d8231f317e35f4;hpb=438596897ebbe25a07e1c82085cfbc5bdb00f09e;p=ghc-hetmet.git

diff --git a/ghc/compiler/utils/Maybes.lhs b/ghc/compiler/utils/Maybes.lhs
index 98efdb7..6dd9251 100644
--- a/ghc/compiler/utils/Maybes.lhs
+++ b/ghc/compiler/utils/Maybes.lhs
@@ -5,9 +5,10 @@
 
 \begin{code}
 module Maybes (
---	Maybe(..), -- no, it's in 1.3
+	Maybe2(..), Maybe3(..),
 	MaybeErr(..),
 
+	orElse, 
 	mapMaybe,
 	allMaybes,
 	firstJust,
@@ -29,6 +30,21 @@ module Maybes (
 #include "HsVersions.h"
 
 import Maybe( catMaybes, mapMaybe )
+
+
+infixr 4 `orElse`
+\end{code}
+
+
+%************************************************************************
+%*									*
+\subsection[Maybe2,3 types]{The @Maybe2@ and @Maybe3@ types}
+%*									*
+%************************************************************************
+
+\begin{code}
+data Maybe2 a b   = Just2 a b   | Nothing2  deriving (Eq,Show)
+data Maybe3 a b c = Just3 a b c | Nothing3  deriving (Eq,Show)
 \end{code}
 
 
@@ -96,6 +112,10 @@ returnMaybe = Just
 
 failMaybe :: Maybe a
 failMaybe = Nothing
+
+orElse :: Maybe a -> a -> a
+(Just x) `orElse` y = x
+Nothing  `orElse` y = y
 \end{code}
 
 Lookup functions
@@ -165,3 +185,4 @@ returnMaB v = Succeeded v
 failMaB :: err -> MaybeErr val err
 failMaB e = Failed e
 \end{code}
+