Function alpha_num

pub fn alpha_num<Input>() -> impl Parser<Input, Output = char, PartialState = ()>
where
    Input: Stream<Token = char>,

Parses either an alphabet letter or digit according to std::char::is_alphanumeric.

use combine::Parser;
use combine::parser::char::alpha_num;
assert_eq!(alpha_num().parse("A"), Ok(('A', "")));
assert_eq!(alpha_num().parse("1"), Ok(('1', "")));
assert!(alpha_num().parse("!").is_err());