Function winnow::combinator::peek

pub fn peek<I: Stream, O, E: ParseError<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::character::alpha1;

let mut parser = peek(alpha1);

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