:: Ord a => [a] -> [a] -package:html-entities -package:safe is:exact -package:Cabal-syntax -package:mono-traversable -package:ghc -package:lifted-base -package:incipit-base -package:statistics -package:base-prelude -package:errors -package:imports 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.