Function winnow::combinator::peek

pub fn peek<I: Stream, O, E: ParserError<I>, F>(f: F) -> impl Parser<I, O, E>
where
    F: Parser<I, O, E>,

Tries to apply its parser without consuming the input.

Example

use winnow::combinator::peek;
use winnow::ascii::alpha1;

let mut parser = peek(alpha1);

assert_eq!(parser.parse_peek("abcd;"), Ok(("abcd;", "abcd")));
assert_eq!(parser.parse_peek("123;"), Err(ErrMode::Backtrack(InputError::new("123;", ErrorKind::Slice))));