My function's being dumb.

Hi.

I'm trying to write a C++ program for class that'll take two numbers and see if one is a multiple of the other. I'm doing this with a function and by repeatedly subtracting the bigger number by the smaller one until the value left over is "0" or lower.

However, I am running into quite a stupid problem. I can get it to display the left over number and it'll either output "0" or lower letting me know that the code worked.

As soon as I put in an "if" statement and a "cout << " to display either "True" or "False", it just... resets the number back to '0'? wtf?

This is what I have so far:

Code:

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//Page 274
//Question 6.20


#include <iostream>

using namespace std;

int multiple(int a, int b){
    int c;
    if(b>a){
            c = b;
   
            while(c>0){
                      c-=a;
            }
    }else if(b<a){
            c = a;
           
            while(c>0){
                      c-=b;
            }
    }
   
    return (c);
   
}

int main(){
    int numone, numtwo;
    int ismultiple;
   
    cout << "Enter a number: ";
    cin >> numone;
    cout << "Enter another number: ";
    cin >> numtwo;
   
    ismultiple = multiple(numone, numtwo);
   
    if(ismultiple=0)cout << "True.\n";
   
    cout << ismultiple << endl;
 
    return 0; 
}

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Now comment out that "if(ismultiple=0)cout << "True.\n";" line and the code works. It displays the right number.

Am I doing something wrong?

Code:

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if(ismultiple==0)cout << "True.\n";

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On your multiple function, what gets returned when a==b?

'c' does.

It starts off with 'c' being assigned the bigger number, and then it's subtracted by the smaller number until it's 0 or less.

Is that correct?
What is neither number is bigger?
Is a number considered to be a multiple of itself?

Quote:

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Originally Posted by Yart

'c' does.

It starts off with 'c' being assigned the bigger number, and then it's subtracted by the smaller number until it's 0 or less.

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As written, it will just return a random number, likely 0 or the value of a variable from a previously called and returned function.

Quote:

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Originally Posted by King Mir

As written, it will just return a random number, likely 0 or the value of a variable from a previously called and returned function.

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The thing is though, it's not.

Here's some output:

Code:

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Enter a number: 3
Enter another number: 5
0

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Now if I remove that one if statement with the cout in the end, it looks like this:

Code:

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Enter a number: 3
Enter another number: 5
-1

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Now I want to take that -1 and go "Oh! It's false!", anything below 0. If it's 0 though, then go "Oh! It's true!"



Why would that one practically irrevalent line screw up the entire thing? It's not changing anything...

Quote:

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Originally Posted by Yart

The thing is though, it's not.

Here's some output:

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Dino asked "what gets returned when a==b?" and I notice that your sample output deals with another case.

Quote:

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Originally Posted by Yart

Now I want to take that -1 and go "Oh! It's false!", anything below 0. If it's 0 though, then go "Oh! It's true!"

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I suggest that you rename multiple to isMultiple (or is_multiple), and change its return type to bool. If you do not actually need to use a loop for educational purposes, use an arithmetic operator related to division.

Am I missing something here? Surely you just need to use the % operator?

Quote:

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Originally Posted by Yart

Now I want to take that -1 and go "Oh! It's false!", anything below 0. If it's 0 though, then go "Oh! It's true!"

Why would that one practically irrevalent line screw up the entire thing? It's not changing anything...

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NeonBlack already gave you the answer in the very first reply.
You're using = (assignment) instead of == (comparison).