Function combine::parser::char::alpha_num

pub fn alpha_num<I>() -> AlphaNum<I> where
    I: Stream<Item = char>,
    I::Error: ParseError<I::Item, I::Range, I::Position>, 

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());