:: Ord a => [a] -> [a] -package:list-t -package:extra -package:amazonka-core -package:lifted-base -package:lens -package:ghc -package:integration -package:basement -package:vector-algorithms -package:safe package:parsers -is:exact is:exact
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.