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Define intersectionWith.

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Rob Rix 2015-12-14 17:00:30 -05:00
parent 253f21d885
commit 1e7dc0ff98
1 changed files with 4 additions and 0 deletions
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4
src/OrderedMap.hs
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@ -9,6 +9,7 @@ module OrderedMap (
, empty
, union
, unions
, intersectionWith
) where
data OrderedMap key value = OrderedMap { toList :: [(key, value)] }
@ -42,3 +43,6 @@ union (OrderedMap a) (OrderedMap b) = OrderedMap $ a ++ filter (not . (`elem` ex
unions :: Eq key => [OrderedMap key value] -> OrderedMap key value
unions = foldl union empty
intersectionWith :: Eq key => (a -> b -> c) -> OrderedMap key a -> OrderedMap key b -> OrderedMap key c
intersectionWith combine (OrderedMap a) (OrderedMap b) = OrderedMap $ a >>= (\ (key, value) -> maybe [] (pure . ((,) key) . combine value) $ Prelude.lookup key b)