Function `peek`

fn peek<I: Clone, F>(parser: F) -> impl Parser<I, Output = <F as Parser<I>>::Output, Error = <F as Parser<I>>::Error>
where
    F: Parser<I>

Tries to apply its parser without consuming the input.

# use nom::{Err,error::ErrorKind, IResult, Parser};
use nom::combinator::peek;
use nom::character::complete::alpha1;
# fn main() {

let mut parser = peek(alpha1);

assert_eq!(parser.parse("abcd;"), Ok(("abcd;", "abcd")));
assert_eq!(parser.parse("123;"), Err(Err::Error(("123;", ErrorKind::Alpha))));
# }