fn start_main() -> i64 {
    print("first: ");
    let invalid: result<f32> = parse_f32(read_line());
    if (invalid::ok) {
        return 1;
    }
    print(invalid::error::code);
    print("\nsecond: ");
    let valid: result<f64> = parse_f64(read_line());
    if (valid::ok) {
        if (format_f64(0.5) not match "0.5") { return 2; }
        if (format_f32(1.0000000596046448) not match "1.00000012") { return 3; }
        print(format_f64(valid::value + 1.0));
        print("\n");
        return 0;
    }
    return 4;
}