:: Ord a => [a] -> [a] -package:html-entities -package:Cabal-syntax -package:witherable -package:lens -package:base-prelude -package:statistics -package:basement -package:ghc -package:errors -package:extra -package:vector package:parsers -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.