:: Ord a => [a] -> [a] is:exact -package:stm-containers -package:errors -package:Cabal -package:safe -package:imports -package:extra -package:lifted-base -package:vector-algorithms -package:generic-deriving -package:basement -package:base-prelude 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.