Thread: What am I doing wrong?

I am trying to get this program to display an error message when the user inputs a zero for the base of an exponent. However, whenever I compile the program the program does not display an error message when I type in zero. I have looked over this code backwards and forwards but still can't find out what is wrong. The line in question is line sixty-four with the expression:

if((num1 == 0)&&(num2 <=0)); {
printf("That is not an acceptable value!\n");
break; }

Can someone please help me? Thanks

Code:

#include <stdio.h>
#include <math.h>

int menu(void);

int main(void) {
   int selection,num1,num2,ans,fans;
   selection = menu();
   while(selection != 8)  {
      switch(selection) {
          case 1: printf("Enter 1st number: ");
                  scanf("&#37;d", &num1);
                  printf("Enter 2nd number: ");
                  scanf("%d", &num2);
                  ans = num1 + num2;
                  printf("%d + %d = %d\n",num1,num2,ans);
                  break;
          case 2: printf("Enter 1st number: ");
                  scanf("%d", &num1);
                  printf("Enter 2nd number: ");
                  scanf("%d", &num2);
                  ans = num1 - num2;
                  printf("%d - %d = %d\n",num1,num2,ans);
                  break;
          case 3: printf("Enter 1st number: ");
                  scanf("%d", &num1);
                  printf("Enter 2nd number: ");
                  scanf("%d", &num2);
                  ans = num1 * num2;
                  printf("%d * %d = %d\n",num1,num2,ans);
                  break;
          case 4: printf("Enter 1st number: ");
                  scanf("%d", &num1);
                  printf("Enter 2nd number: ");
                  scanf("%d", &num2);
                  if(num2 == 0) {
                  printf("Zero is not an acceptable value!\n");
                  break; }
                  fans =(float)num1/num2;
                  printf("%d / %d = %2d\n",num1,num2,fans);
                  break;
          case 5: printf("Enter 1st number: ");
                  scanf("%d", &num1);
                  ans = abs(num1);
                  printf("|%d| = |%d|\n",num1,ans);
                  break;
          case 6: printf("Enter 1st number: ");
                  scanf("%d",&num1);
                  if(num1 < 0){
                  printf("You cannot enter in a negative value!\n");
                  break; }
                  fans = sqrt(num1);
                  printf("sqrt(%d) = %d\n",num1,fans);
                  break;
          case 7: printf("Enter base: ");
                  scanf("%d", &num1);
                  printf("Enter exponent: ");
                  scanf("%d", &num2);
                  if((num1 == 0)&&(num2 <= 0)) {
                  printf("That is not an acceptable value!\n");
                  break; }
                  fans = pow(num1, num2);
                  printf("%d ^ %d = %d\n",num1,num2,fans);
                  break;
         default: printf("%d is not a valid selection\n", selection);
       }
       selection = menu();
    }
    printf("Bye!\n");
  }


  int menu(void) {
      int choice;
      printf("1 Add\n");
      printf("2 Subtract\n");
      printf("3 Multiply\n");
      printf("4 Divide\n");
      printf("5 Absolute Value\n");
      printf("6 Square Root\n");
      printf("7 Powers\n");
      printf("8 Quit\n");
      printf("Enter a Selection: ");
      scanf("%d", &choice);
      return choice;
  }

Perhaps you meant
if (num1 == 0 || num2 <= 0)
If num2 is equal to 0 OR num2 is less or equal to 0.
Also suggest you try indenting a little bit better.

Like this;

Code:

                  if(num2 == 0) {
          printf("Zero is not an acceptable value!\n");
                  break; }

The printf have a lesser indentation level than the preceding if, which makes it even more confusing. For every block, you should indent another level, so:

Code:

if (num2 == 0) {
    printf("Zero is not an acceptable value!\n");
    break;
}

So it should look something like that.
Placing an ending bracket } at the same line as some other code is also not a good idea. It hurts readability.

I could also suggest you try to learn some more from here:
http://cpwiki.sf.net/User:Elysia/Indentation

if((num1 == 0)&&(num2 <=0)); /* will execute only when both expressions are true */

if((num1 == 0) || (num2 <=0)); /* will execute when either expression is true */

Originally Posted by skaldicpoet9

Hmm, when I try to compile it with the code if((num1 ==0) || (num <=0));
it still doesn't display the error message when I type zero though, it only displays it after I type in the second number as a negative or zero.

I believe you want it to immediately print an error when you enter 0 for the first number?
If yes, then recheck your code because that's not what it's doing. It's checking for valid input after you've entered both numbers.

I'd also like to see you fix the indentation a bit.

Originally Posted by skaldicpoet9

it must have got messed up when I pasted it.

To not mess up - use only spaces or only tabs for indentation. do not mix them.

I don't see any tabs in the original code, though, only spaces.