Change implementation of intersectBy

Currently, intersectBy eq xs [] takes O(length xs) time to calculate and returns | on (x : |). The proposed change,

intersectBy             :: (a -> a -> Bool) -> [a] -> [a] -> [a]
intersectBy _  [] _     =  []
intersectBy _  _  []    =  []
intersectBy eq xs ys    =  [x | x <- xs, any (eq x) ys]

makes this an O(1) operation and returns [] for infinite or partial (... : |) lists xs. The first equation is necessary to retain intersectBy _ [] | = [].

Trac metadata

Trac field	Value
Version	6.12.3
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	libraries/base
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