fn push_digit(state: &mut State, ch: char) {
    if let Some(v) = ch.to_digit(16) {
        state.stack.push(v as i64);
    }
}
// push_digit takes a character and pushs it onto the stack as a digit
push_digit takes a character and pushs it onto the stack as a digit
push_digit takes a character and pushs it onto the stack as a digit
fn push_digit(state: &mut State, ch: char) {
    if let Some(v) = ch.to_digit(16) {
        state.stack.push(v as i64);
    }
}
fn push_digit ( state : & mut State , ch : char ) { if let Some ( v ) = ch . to_digit ( 16 ) { state . stack . push ( v as i64 ) ; } }
push_digit takes a character and pushs it onto the stack as a digit
push_digit takes a character and pushs it onto the stack as a digit
state
&mut State
ch
char
state
&mut State
ch
char