I have been trying to figure out why the output of the code below is 2 2 but can't seem to figure out why. I get that the else statement is getting executed but from what I've read I can't understand why the first print doesn't get executed.

#include <stdio.h>
#include <stdlib.h>

int main()
{
    int x = 1, y = 1;

    if(x   == y  )
        printf("%d%d", x--, y--);
    else
        printf("%d%d", x,y);
    return 0;
}

Originally I expected the output to be 0 0

I have played around with changing the values and the operators and each time the decrement print never executed. From what I can tell from reading on the topic decrementing inside a print should be possible but I'm not sure what is making it not execute.

CodePudding user response：

The if block is being executed.

In the condition if(x == y ), the current value of x is compared with the current value of y. Both are 1 so the comparison is true, and both x and y are incremented as a side effect.

So then this statement runs:

printf("%d%d", x--, y--);

Which prints the current values of x and y which are both 2, and both are decremented as a side effect. If you were to print both after this, you would see that both are 1.

CodePudding user response：

In order to understand your code, you might do the following:

int main()
{
    int x = 1, y = 1;

    printf("x=%d, y=%d", x,y);
    if(x   == y  )
    {
        printf("x=%d, y=%d", x,y);
        printf("x--=%d, y--=%d", x--, y--);
        printf("x=%d, y=%d", x,y);
    }
    else
        printf("x=%d, y=%d", x,y);
    return 0;
}

CodePudding user response：

#include <stdio.h>
#include <stdlib.h>

int main()

{
   int x = 1, y = 1;

   if(x   == y  )               // here x and y become 2
    printf("%d%d", x--, y--);   // x with postfix decrement x and
                                //  returns the initial value 
   else
    printf("%d%d", x,y);
  return 0;
}

lot of help You get my recomendation use prefix x