Function combine::parser::byte::upper

pub fn upper<I>() -> Upper<I> where
    I: Stream<Item = u8>,
    I::Error: ParseError<I::Item, I::Range, I::Position>, 

Parses an uppercase ASCII letter (A–Z).

use combine::Parser;
use combine::parser::byte::upper;
assert_eq!(upper().parse(&b"A"[..]), Ok((b'A', &b""[..])));
assert!(upper().parse(&b"a"[..]).is_err());