:: Ord a => [a] -> [a] -package:statistics -package:safe -package:vector-algorithms -package:lifted-base -package:imports -package:ghc -is:exact -package:incipit-base -package:extra -package:amazonka-core -package:generic-deriving 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.