**takeWhile** -text -bytestring

takeWhile, applied to a predicate p and a list xs, returns the longest prefix (possibly empty) of xs of elements that satisfy p:
> takeWhile (< 3) [1,2,3,4,1,2,3,4] == [1,2]
> takeWhile (< 9) [1,2,3] == [1,2,3]
> takeWhile (< 0) [1,2,3] == []
*O(i)* applied to a predicate p and a sequence xs, returns the longest prefix (possibly empty) of xs of elements that satisfy p.

*O(i)* applied to a predicate p and a sequence xs, returns the longest suffix (possibly empty) of xs of elements that satisfy p.
takeWhileR p xs is equivalent to reverse (takeWhileL p (reverse xs)).