Program Is Outputting Data as an int not double?

[PiggiesGoSqueal]

I made a program that converts money from yen, kroner, and/or pounds to USD. However, for some reason it outputs the result as an int rather than double for kroner and pounds. I know I could use setprecision() but I shouldn't need to use it for this.

Could you please tell me what I'm doing wrong or give me a hint? Thanks!

/*
Program Name: MoneyConversion.cpp
Program Purpose:
- This is an exercise for the programming textbook for C++ I'm learning from.

Program Goal:
- Write a program that converts yen ('y'), kroner ('k'), and pounds ('p')
  into dollars.
*/
#include <iostream>

int main() {
    double money = 0.0;
    char symbol = ' ';
    std::cout << "Input the balance of money you would like to convert followed by the symbol sign (y, k, or p): ";
    std::cin >> money >> symbol;

    double USD = 0.0;

    // Yen to USD
    if (symbol == 'y') {
        USD = money * 0.0094;
    }
    // Kroner to USD
    else if (symbol == 'k') {
        USD = money * 0.11;
    }
    // Pounds to USD
    else if (symbol == 'p') {
        USD = money * 1.22;
    }
    // Anything Else:
    else {
        std::cout << "Error. Incorrect money type input.\n";
        exit(EXIT_FAILURE);
    }

    std::cout << "You will receive " << USD << " USD in return for your " << money << symbol << '\n';
    // It should output a double not int. But does int for k and p.
    // BUG ^
    
    return 0;
}

[zapshe]

I get decimal outputs when I run it. There's nothing wrong with the code, perhaps an old compiler?

[Ganado]

Wait what exactly is the issue?

Input the balance of money you would like to convert followed by the symbol sign (y, k, or p): 11.44y
You will receive 0.107536 USD in return for your 11.44y

Edit: Are you saying you want it to show a .0 when the output happens to be a whole number?

[deleted account xyzzy]

I tried your code in VS 2019 and got the following output:

Input the balance of money you would like to convert followed by the symbol sign (y, k, or p): 18 y
You will receive 0.1692 USD in return for your 18y

Could you post a sample output? I'd bet you are entering a number that after calculation ends up with a decimal portion that is so small it gets trimmed off on output.

If you are going to use exit() and EXIT_FAILURE you should include <cstdlib>. A future version of your compiler may remove the implicit inclusion.

[Ganado]

Obligatory warning: Money amounts should never be stored as floating point (double)! The only things here that can be stored as a double is the exchange rate itself, and the transient multiplication result before it is rounded and converted back into a currency.

Currency exchange rate rounding rules seem to say "apply the multiplication, and then round to 2 decimal places".
https://help-2018r1.acumatica.com/Wiki/ShowWiki.aspx?pageid=749a8ca0-64b6-4e9c-b0dd-d0b9fccf5578

57.785 EUR becomes 57.79

57.354 EUR becomes 57.35 EUR.)

Other countries/zones might have different rules, but I'd say the above is probably good enough for most purposes.


For example, here is a better way to store a currency. Note that this is still far from perfect, because you'll need something else to handle overflow, and it's not very user-input friendly, but it's a start.

#include <iostream>
#include <iomanip>

using currency_type = long long int;
struct Currency {
    currency_type amount;  
};

std::ostream& print_usd(std::ostream& os, const Currency& currency)
{
    return os << currency.amount / 100 << '.'
        << std::setfill('0') << std::setw(2)
        << currency.amount % 100;
}

int main() {

    Currency c { 123407 };   
    print_usd(std::cout, c) << '\n';
    
    Currency c2 { 409 };
    print_usd(std::cout, c2) << '\n';
}

1234.07
4.09

[PiggiesGoSqueal]

Here are some examples of output:

Input the balance of money you would like to convert followed by the symbol sign (y, k, or p): 100k
You will receive 11 USD in return for your 100k

zapshe wrote:

I get decimal outputs when I run it. There's nothing wrong with the code, perhaps an old compiler?

Ganado wrote:

Edit: Are you saying you want it to show a .0 when the output happens to be a whole number?

Furry Guy wrote:

Could you post a sample output? I'd bet you are entering a number that after calculation ends up with a decimal portion that is so small it gets trimmed off on output.

Oh yeah it does work... I guess I just didn't realize the numbers I input were whole numbers. I thought they were being rounded to the nearest whole number yesterday. Whoops. Sorry everyone. Post solved. Thanks :P

Furry Guy wrote:

If you are going to use exit() and EXIT_FAILURE you should include <cstdlib>. A future version of your compiler may remove the implicit inclusion.

Oh okay, thank you for letting me know!

Ganado wrote:

Obligatory warning: Money amounts should never be stored as floating point (double)! The only things here that can be stored as a double is the exchange rate itself, and the transient multiplication result before it is rounded and converted back into a currency.

Currency exchange rate rounding rules seem to say "apply the multiplication, and then round to 2 decimal places".
https://help-2018r1.acumatica.com/Wiki/ShowWiki.aspx?pageid=749a8ca0-64b6-4e9c-b0dd-d0b9fccf5578
57.785 EUR becomes 57.79
57.354 EUR becomes 57.35 EUR.)


Other countries/zones might have different rules, but I'd say the above is probably good enough for most purposes.


For example, here is a better way to store a currency. Note that this is still far from perfect, because you'll need something else to handle overflow, and it's not very user-input friendly, but it's a start.
<code>

Ah okay, thanks for letting me know.