The
dropWhileEnd function drops the largest suffix of a list in
which the given predicate holds for all elements.
Laziness
This function is lazy in spine, but strict in elements, which makes it
different from
reverse . dropWhile p
. reverse, which is strict in spine, but lazy in
elements. For instance:
>>> take 1 (dropWhileEnd (< 0) (1 : undefined))
[1]
>>> take 1 (reverse $ dropWhile (< 0) $ reverse (1 : undefined))
*** Exception: Prelude.undefined
but on the other hand
>>> last (dropWhileEnd (< 0) [undefined, 1])
*** Exception: Prelude.undefined
>>> last (reverse $ dropWhile (< 0) $ reverse [undefined, 1])
1
Examples
>>> dropWhileEnd isSpace "foo\n"
"foo"
>>> dropWhileEnd isSpace "foo bar"
"foo bar"
>>> dropWhileEnd (> 10) [1..20]
[1,2,3,4,5,6,7,8,9,10]