intersectBy is:exact

The intersectBy function is the non-overloaded version of intersect. It is productive for infinite arguments only if the first one is a subset of the second.

The intersectBy function is the non-overloaded version of intersect.

Generic version of intersect

intersectBy is essentially a filtering operation that retains only those elements in the first stream that are present in the second stream.

>>> Stream.toList $ Stream.intersectBy (==) (Stream.fromList [1,2,2,4]) (Stream.fromList [2,1,1,3])
[1,2,2]

>>> Stream.toList $ Stream.intersectBy (==) (Stream.fromList [2,1,1,3]) (Stream.fromList [1,2,2,4])
[2,1,1]

intersectBy is similar to but not the same as joinInner:

>>> Stream.toList $ fmap fst $ Stream.joinInner (==) (Stream.fromList [1,2,2,4]) (Stream.fromList [2,1,1,3])
[1,1,2,2]

Space: O(n) where n is the number of elements in the second stream. Time: O(m x n) where m is the number of elements in the first stream and n is the number of elements in the second stream. Pre-release

Take the intersection of two tries, using a function to resolve collisions.

intersectBy returns a subsequence of the first stream which intersects with the second stream. Note that this is not a commutative operation unlike a set intersection, because of duplicate elements in the stream the order of the streams matters. This is similar to intersectBy. Note that intersectBy is a special case of innerJoin.

>>> f s1 s2 = Stream.fold Fold.toList $ Stream.intersectBy (==) (Stream.fromList s1) (Stream.fromList s2)

>>> f [1,3,4,4,5] [2,3,4,5,5]
[3,4,4,5]

First stream can be infinite, the second stream must be finite and must be capable of multiple evaluations. Space: O(n) where n is the number of elements in the second stream. Time: O(m x n) where m is the number of elements in the first stream and n is the number of elements in the second stream. Pre-release

Overloaded version of intersect.

O(n*m). Non-overloaded version of intersect.