From: sof <unknown>
Date: Sun, 18 May 1997 04:56:05 +0000 (+0000)
Subject: [project @ 1997-05-18 04:56:05 by sof]
X-Git-Tag: Approximately_1000_patches_recorded~648
X-Git-Url: http://git.megacz.com/?a=commitdiff_plain;h=62a2c335be9c3f33cd7d459d5403ea94b148c5ea;p=ghc-hetmet.git

[project @ 1997-05-18 04:56:05 by sof]
new function: mapMaybe
---

diff --git a/ghc/compiler/utils/Maybes.lhs b/ghc/compiler/utils/Maybes.lhs
index a3834fd..2542141 100644
--- a/ghc/compiler/utils/Maybes.lhs
+++ b/ghc/compiler/utils/Maybes.lhs
@@ -12,6 +12,7 @@ module Maybes (
 --	Maybe(..), -- no, it's in 1.3
 	MaybeErr(..),
 
+	mapMaybe,
 	allMaybes,
 	firstJust,
 	expectJust,
@@ -80,6 +81,12 @@ allMaybes (Nothing : ms) = Nothing
 allMaybes (Just x  : ms) = case (allMaybes ms) of
 			     Nothing -> Nothing
 			     Just xs -> Just (x:xs)
+
+mapMaybe :: (a -> Maybe b) -> [a] -> [b]
+mapMaybe f [] = []
+mapMaybe f (x:xs) = case f x of
+			Just y  -> y : mapMaybe f xs
+			Nothing -> mapMaybe f xs
 \end{code}
 
 @firstJust@ takes a list of @Maybes@ and returns the