How to make change calculator more simple

Question

Okay so classes got out a month ago and fall semester starts back up in 3 weeks. I wanted to do the homework in the book that we were never assigned. This one question gotta got me stuck because its in the second chapter. Its a program to give change back (the 92 cents is a compile time initialization). My question is... Is there any way to make this program more "dummy downed" than it is. And also I had to put (int) in front of my assignment of what anQuarter, anDime, etc were. Otherwise I was getting decimals afterwards. Why is that? Can an experienced programmer explain?

Also, the chapter talked about MOD so that is why I used it. This is before calling class methods are introduced and obviously before loops and arrays. So I couldnt use any of those tools. Supposed to be just a very basic "cave man" program...

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ConsoleApplication273
{
    class Program
    {
        static void Main(string[] args)
        {
        double change = 0.92;

        double quarter = 0.25;
        double dime = 0.10;
        double nickel = 0.05;
        double pennies = 0.01;

        double anQuarter = (int)(change / quarter);
        double anDime = (int)((change % quarter) / dime);
        double anNickel = (int)(((change % quarter) % dime) / nickel);
        double anPennies = (int)((((change % quarter) % dime) % nickel) / pennies);

        Console.WriteLine("The amount of quarters are....{0}", anQuarter);
        Console.WriteLine("The amount of dimes are....{0}", anDime);
        Console.WriteLine("The amount of nickels are....{0}", anNickel);
        Console.WriteLine("The amount of pennies are....{0}", anPennies);
        }
    }
}

What exactly is your question? This looks about as straight-forward as it gets. — Jonathon Reinhart, Aug 01 '13 at 22:36
Try using decimal instead of double since accuracy is important. — LarsTech, Aug 01 '13 at 22:37
Ask this kind of questions on `codereview.stackexchange.com`. — Tim Schmelter, Aug 01 '13 at 22:37
A couple people have suggested using `decimal` which is excellent advice. You might consider instead using integers and redoing everything in terms of pennies. You're already casting to int all over the place; why not just do it all in ints in the first place? — Eric Lippert, Aug 01 '13 at 22:39
there is one fatal flaw here, and its not in your code. "I wanted to do the homework in the book that we were never assigned." — invertigo, Aug 01 '13 at 22:44
This question appears to be off-topic because it belongs on CodeReview.SE — Robert Rouhani, Aug 02 '13 at 07:05

score 7 · Accepted Answer · edited May 23 '17 at 11:50

At the very least employ decimal: Difference between decimal, float and double in .NET?

Then removing the duplication of code: See it live on http://ideone.com/ZY9qBm

using System;

class Program
{
    static void Main()
    {
        decimal change    = 0.92m;

        var coins = new [] { // ordered
            new { name = "quarter", nominal   = 0.25m }, 
            new { name = "dime", nominal      = 0.10m },
            new { name = "nickel", nominal    = 0.05m },
            new { name = "pennies", nominal   = 0.01m }
        };

        foreach (var coin in coins)
        {
            int count = (int) (change / coin.nominal);
            change -= count * coin.nominal;

            Console.WriteLine("{0} {1}", count, coin.name);
        }
    }
}

Prints

3 quarter
1 dime
1 nickel
2 pennies

Rewrote the coin distribution to get rid of code duplication. For fun, also see http://stackoverflow.com/questions/15532840/any-better-way-to-implement-this/15534025#15534025 — sehe, Aug 01 '13 at 22:43
+1 for the anonymous structure. I never thought to use them this way. — Steve, Aug 02 '13 at 00:03

score 2 · Answer 2 · answered Aug 01 '13 at 22:45

And also I had to put (int) in front of my assignment of what anQuarter, anDime, etc were. Otherwise I was getting decimals afterwards. Why is that? Can an experienced programmer explain

The (int) is converting the value in the expression to integer type. Using type casts like this are useful ways of converting from one data type to another. In this case, your calculation is resulting in a double data type. Casting this to int is the easiest way of knocking off all the decimal digits without rounding.

That makes sense. I understand that now. – Zoro Aug 01 '13 at 22:52 — Zoro, Aug 01 '13 at 22:52

score 1 · Answer 3 · answered Aug 01 '13 at 22:41

A few thoughts...

I'd recommend decimal over double - with decimal, you get exact decimal representations, which is generally what you want with money. With double (or float), you get binary representations, which aren't always equal.

The reason you're getting decimals when you divide is that a double divided by a double will give you a double in C#. If you want to get int, you either have to truncate it like you're doing, or start with ints in the first place. An int divided by an int gets you an int.

To make the whole thing simpler, you can treat everything as whole numbers of cents, like:

int change = 92;

int quarter = 25;
int dime = 10;
int nickel = 5;
int pennies = 1;

int anQuarter = change / quarter;
int anDime = ((change % quarter) / dime);
int anNickel = (((change % quarter) % dime) / nickel);
int anPennies = ((((change % quarter) % dime) % nickel) / pennies);

For readability though, you can do it lots of different ways. One way (probably not the best way) is to just keep reducing the amount owed until you get to zero.

int anQuarter = 0, anDime = 0, anNickel = 0, anPennies = 0;
while (change >= 25)
{
    anQuarter++;
    change -= 25;
}
while (change >= 10)
{
    anDime++;
    change -= 10;
}
while (change >= 5)
{
    anNickel++;
    change -= 5;
}
while (change >= 1)
{
    anPennies++;
    change -= 1;
}

How to make change calculator more simple

3 Answers3