:: Ord a => [a] -> [a] is:exact -package:imports -package:safe -package:lens -package:ghc -package:witherable -package:base-prelude -package:errors -package:base -package:mono-traversable -package:vector -package:vector-algorithms package:parsers
Take a parser that may consume input, and on failure, go back to where
we started and fail as if we didn't consume input.