type Flag = bool | f64 | int | string

fn parse_percent(value string) f64 {
	f_val := value.f64()
	if f_val >= 0 && f_val <= 100 {
		return f_val
	} else {
		return 0
	}
}

fn parse_option(str string, validator fn (string) ?Flag) ?Flag {
	return validator(str)
}

fn main() {
	t := parse_option('45', parse_percent)?
	println(t)
}