:: Ord a => [a] -> [a] -package:witherable -package:Cabal-syntax -package:statistics -package:safe -package:extra -package:vector-algorithms -package:base-prelude -package:integration is:exact -package:basement -package:ghc 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.