From 4299243f0470c1892d7472edcd41cd56f41114ce Mon Sep 17 00:00:00 2001
From: sof <unknown>
Date: Tue, 21 Oct 1997 20:31:47 +0000
Subject: [PATCH] [project @ 1997-10-21 20:31:47 by sof] unionBy: remove
duplicates in second argument (required for the following invariant to hold:
if the first list argument contain no duplicates, then the result of applying
unionBy doesn't either)
---
ghc/lib/required/List.lhs | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/ghc/lib/required/List.lhs b/ghc/lib/required/List.lhs
index 444b2e90bc2c..d48c5bf9ddf4 100644
--- a/ghc/lib/required/List.lhs
+++ b/ghc/lib/required/List.lhs
@@ -8,7 +8,7 @@
module List (
{-
This list follows the type signatures for the
- standard List interface.
+ standard List interface. -- 8/97
-}
elemIndex, elemIndices,
find, findIndex, findIndices,
@@ -16,10 +16,10 @@ module List (
delete, deleteBy, (\\), deleteFirstsBy,
union, unionBy,
intersect, intersectBy,
+ intersperse, transpose, partition,
group, groupBy,
inits, tails,
isPrefixOf, isSuffixOf,
- intersperse, transpose, partition,
mapAccumL, mapAccumR,
sort, sortBy,
insertBy,
@@ -117,7 +117,7 @@ union :: (Eq a) => [a] -> [a] -> [a]
union = unionBy (==)
unionBy :: (a -> a -> Bool) -> [a] -> [a] -> [a]
-unionBy eq xs ys = xs ++ foldl (flip (deleteBy eq)) ys xs
+unionBy eq xs ys = xs ++ foldl (flip (deleteBy eq)) (nubBy eq ys) xs
intersect :: (Eq a) => [a] -> [a] -> [a]
intersect = intersectBy (==)
--
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