Why does function return two values despite returning 0?

Question

I am making a calculator in c, everything works except when using the division command "/"

When a number is divided by 0 it should print out "NaN" and then exiting the program. However the output is: NaN0.0

Meaning that the function is also returning the value of the float despite using the return 0 command.

How do i make it so that the function just returns "NaN"?

float calc(float param1, char operator1, float param2){
#include <math.h>

float result;


switch(operator1){

        case '+':
                result = param1 + param2;
                return result;
break;

        case '-':
                result = param1 - param2;
                return result;
break;

        case '*':
                result = param1 * param2;
                return result;
break;

        case'/':
                if(param2 == 0){printf("NaN"); //Issue here
                return 0;
                }
                else{
        result = param1 / param2;}
        return result;
break;

        case '^':
        result = pow(param1, param2);
        return result;
}

}

You definitely should not have a `#include` line *inside* your function. — Karl Knechtel, Nov 20 '21 at 15:49
That said, your code shows `NaN` and then `0.0` because you display `NaN` and then return `0.0` to the calling code, which displays that. — Karl Knechtel, Nov 20 '21 at 15:50

score 0 · Accepted Answer · edited Nov 21 '21 at 00:51

I'd need the full code to be able to be 100% certain, but I think what you are doing is the following:

printf('%lf', calc(0, '/', 0));

So, you're outputting the result of the execution of the "calc" command on screen, which is here: 0

But, before returning this 0 value, you're also printing the value "NaN" to screen.

So, by doing:

printf('%lf', calc(0, '/', 0));

You're telling the computer:

Compute the result of calc(0, '/', 0) : It prints NaN during the execution
Then, print the result, which is 0

That's why your computer is showing NaN 0

The function is not returning two values. It's indeed returning only one, but also printing NaN.

To fix that, just remove the print and return a special value that can be understood as NaN in the rest of your code.

Why does function return two values despite returning 0?

1 Answers1