Passing one variable by reference and "returning" two variables

Question

So I am trying to pass in one variable, the money variable, and break it into two variables. I am stuck and trying to figure out how to pass back two values when I only passed in one. I am supposed to get a double value of money from the user and split it into two int values. So for example I get a value like 3.45 and split it up and print out the message, "There is 3 dollars and 45 cents in $3.45". I understand pass by reference, but I am just trying to figure out like I said how to get two variables back. And I can ONLY pass in the money variable to the method I know my program is not right. Just looking for some ideas and explanations on how to do this. Thanks

 using System;

 static class Program
 {
      //Declare any constansts
      const int ONE_HUNDRED = 100;

     static void Main()
     {
         //Declare local variables
         double money = 0;

         //Ask the user to input a money value
         Console.WriteLine("Please enter a money value. (ex. 2.95)");

         //Store the value in a variable
          money = double.Parse(Console.ReadLine());

          //Take the variable and call the SplitMoney method
          SplitMoney(ref money);

          //Display the message
          Console.WriteLine("There are {0:d} and {1:d} cents in ${0:f2}", money, dollars cents);

          Console.ReadLine();
     }//End Main()

      //Split Money Method
      //Purpose: To split the money into dollars and cents
      //Parameters: One double passed by reference
      //Returns: Nothing
      static void SplitMoney(ref double money)
      {
            money = (int)(money * ONE_HUNDRED);
            int dollars = (int)(money / ONE_HUNDRED);
            int cents = (int)(money % ONE_HUNDRED);
      }
   }//End class Program

Duplicate http://stackoverflow.com/questions/748062/how-can-i-return-multiple-values-from-a-function-in-c question covers many possible ways to return multiple values - feel free to pick what you like or opn new question if way you need is not covered (return `Tuple`, return custom type, use `out`/`ref` to return each result) — Alexei Levenkov, Jun 28 '14 at 00:13
An array is often the easiest: `static int[] SplitMoney(decimal money) { return new[] {(int)(money / 100),(int)(money % 100)}; }` — Reactgular, Jun 28 '14 at 00:14

score 3 · Answer 1 · edited Jun 28 '14 at 00:26

3

For your question:

public class SplittedMoney
{
    public int Dollars { get; set; }
    public int Cents { get; set; }
}

You return that. That would be the easiest way.

A somewhat better way may be:

public struct SplittedMoney
{
    public readonly int Dollars;
    public readonly int Cents;

    public SplittedMoney(int dollars, int cents)
    {
        Dollars = dollars;
        Cents = cents;
    }
}

This is better, as a splitted dollar is still a value, so using an immutable struct is the way to go here.

Now, don't use doubles in anything that requires precise decimal calculations. Use decimals instead as they're designed for that task. A double can lose precision is base 10, as it is stored and manipulated in base 2. A decimal is designed to preserve precision in base 10.

Here's a rewrite of SplitMoney using the above struct:

  static SplittedMoney SplitMoney(decimal money)
  {
        var totalCents = (int)(money * 100);
        int dollars = (int)(totalCents / 100);
        int cents = (int)(totalCents % 100);
        return new SplittedMoney(dollars, cents);
  }

edited Jun 28 '14 at 00:26

Jonathan Wilson

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answered Jun 28 '14 at 00:06

Lucas Trzesniewski

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why use a floating point number at all? You could rewrite your class such that `Dollars` and `Cents` are each an `int`. – Jonathan Wilson Jun 28 '14 at 00:11
That would be more cumbersome to manipulate. `System.Decimal` is designed to solve this very problem. – Lucas Trzesniewski Jun 28 '14 at 00:12
1

Using `decimal` to represent `Dollars` means you can have fractional dollars but your struct already represents a fractional dollar in the `Cents` field. It's just kinda odd – Jonathan Wilson Jun 28 '14 at 00:14
Oh you're absolutely right. I misunderstood what you meant. – Lucas Trzesniewski Jun 28 '14 at 00:17
1

The same goes for `Cents`. Does it make *sense* to have fractional cents? In the question, you'll see that cents are represented as an `int`. – Jonathan Wilson Jun 28 '14 at 00:20
Yes it makes sense. Consider the forex market for instance. Right now, 1 Euro = 1.36486 U.S. dollars. You can't just assume there is a round number of cents. Of course, if your app doesn't require it, it would make sense to use an int for cents, it all depends on your needs. But yes as the OP uses ints, I'll go for int as well. – Lucas Trzesniewski Jun 28 '14 at 00:22
You are right overall. I'm just talking about the question. – Jonathan Wilson Jun 28 '14 at 00:23
Sorry if I appeared rude, I didn't mean that at all. Your comments are very constructive. – Lucas Trzesniewski Jun 28 '14 at 00:24
1

Not rude at all. Also, I added an implementation of `SplitMoney` that returns a `SplittedMoney` to your answer. – Jonathan Wilson Jun 28 '14 at 00:26

Jonathan Wilson · Answer 2 · 2014-06-28T00:29:10.953

0

Well, SplitMoney is currently returning 0 values. You could continue to mutate money to contain only the dollar value, and then actually return cents from the method.

  static int SplitMoney(ref double money)
  {
        money = (int)(money * ONE_HUNDRED);
        int dollars = (int)(money / ONE_HUNDRED);
        int cents = (int)(money % ONE_HUNDRED);
        return cents;
  }

Then when you use it:

var moneyCents = SplitMoney(ref money);
Console.WriteLine("money = {0:f2}.{1:f2}", money, moneyCents);

Better yet, you can return a tuple containing both dollars and cents:

  static Tuple<int,int> SplitMoney(double money)
  {
        var totalCents = (int)(money * ONE_HUNDRED);
        int dollars = (int)(money / ONE_HUNDRED);
        int cents = (int)(money % ONE_HUNDRED);
        return Tuple.Create(dollars,cents);
  }

Which would be used as

var splitMoney = SplitMoney(money);
Console.WriteLine("money = {0:f2}.{1:f2} from {2:d}",
    splitMoney.Item1, splitMoney.Item2, money);

edited Jun 28 '14 at 00:29

answered Jun 28 '14 at 00:06

Jonathan Wilson

4,138
1
24
36

2

I should note that `SplitMoney` should probably be rewritten to be a pure function (does not mutate a value outside its scope) that returns a `SplittedMoney` object, as Lucas described in his answer. My solution just requires a small change to your code. – Jonathan Wilson Jun 28 '14 at 00:09
Actually your thought won't work. My statement ahs to be Console.Writeline("There are {0:d} dollars and {1:d} cents in {3:f2)", money, dollars, cents); – Charlie Barber Jun 28 '14 at 00:13
In that case, the answer with `SplittedMoney` is definitely the way to go. The problem with this approach is that the original money value is no longer available since you mutated that variable in your method. – Jonathan Wilson Jun 28 '14 at 00:16
Do you have any other ideas? I am suppose to use doubles and there are no structs used – Charlie Barber Jun 28 '14 at 00:21
I just added an implementation of `SplitMoney` that returns a 2-Tuple – Jonathan Wilson Jun 28 '14 at 00:33

Passing one variable by reference and "returning" two variables

2 Answers2