Function combine::parser::char::upper

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

Parses an uppercase letter according to std::char::is_uppercase.

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