fn digit(b: u8) -> Option<u8> {
    if b >= b'0' && b <= b'9' {
        Some(b - b'0')
    } else {
        None
    }
}
/// Convert ASCII digit to a number
Convert ASCII digit to a number
Convert ASCII digit to a number
fn digit(b: u8) -> Option<u8> {
    if b >= b'0' && b <= b'9' {
        Some(b - b'0')
    } else {
        None
    }
}
fn digit ( b : u8 ) -> Option < u8 > { if b >= b'0' && b <= b'9' { Some ( b - b'0' ) } else { None } }
Convert ASCII digit to a number
Convert ASCII digit to a number
b
u8