:: Ord a => [a] -> [a] -package:list-t -package:mono-traversable -package:witherable -package:lens -package:amazonka-core -package:ghc -is:exact is:exact -package:containers -package:Cabal-syntax -package:Cabal -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.