How to peek and, on success, consume one char only?

[ckoehler]

Something like this:

pub fn my_parser<'s>(input: &mut &'s str) -> PResult<&'s str> {
  // matches on "foo"
  peek("foo").parse_next(input)
  // more here
}

let input = "foobar";
let output = my_parser.parse_next(input).unwrap();
assert_eq!(output, "f");
// only one char consumed
assert_eq!(input, "oobar");

Thanks!

[epage]

peek will backtrack on lack of success, so you should be able to do

pub fn my_parser<'s>(input: &mut &'s str) -> PResult<char> {
  let _ = peek("foo").parse_next(input)?;
  any.parse_next(input)
}

When foo doesn't match, you can do other things like opt, alt, etc.

[ckoehler]

Thanks, that did the trick!