5

I want to know if:

val1 =  val2 = val3 ... = val6

I try this: 

if (val1 == val2 == val3 == val4 == val5 == val6) 
{


}

but it don't work, why?

rmaddy
  • 314,917
  • 42
  • 532
  • 579
Anis
  • 105
  • 5

4 Answers4

18

The == operator only works between pairs of values. When you do this:

val1 == val2 == val3

What's really happening is this:

(val1 == val2) == val3

So if val1 and val2 are equal, the expression in the parenthesis evaluates to true:

true == val3

And then it checks whether true == val3, not whether val1 or val2 == val3. You have to do this instead:

val1 == val2 && val1 == val3

This is getting pretty unwieldy for six variables though. Do you really have six local variables that you have to compare? Perhaps you should store them in an array of some sort. Then you can do:

bool all_equal(int *vals, int length) {
    if (length == 0) {
        return true;
    }
    int first = vals[0];
    for (int i=1; i < length; i++) {
        if (vals[i] != first) {
            return false;
        }
    }
    return true;
}

So instead of:

int val1 = ..., val2 = ..., val3 = ..., val4 = ..., val5 = ..., val6 = ...;
if (val1 == val2 && val2 == val3 && val3 == val4 && val4 == val5 && val5 == val6) {
    ...
}

You would to:

int vals[6] = {..., ..., ..., ..., ..., ...};
if (all_equal(vals, 6)) {
    ...
}
Claudiu
  • 224,032
  • 165
  • 485
  • 680
8

You can't chain the == operator. Do this:

if (val1 == val2 && val2 == val3 && val3 == val4 && val4 == val5 && val5 == val6) {
    // they are all equal
}
rmaddy
  • 314,917
  • 42
  • 532
  • 579
1

Error Issue is already ably explained by other users, I just wanted to share an another approach.

I written a C code using variable number of arguments: 9.9. Variable numbers of arguments I hope you find it interesting

#include<stdio.h>
#include<stdarg.h>     
typedef enum {FALSE, TRUE} boolean;
boolean isAllEqual(int count, ...){   
    va_list ap;  // vlist variable
    int num = 0;
    boolean flag = TRUE;
   //Step2: To initialize `ap` using right-most argument that is `c` 
    va_start(ap, count); 

   //Step3: Now access vlist `ap`  elements using va_arg()
     num = va_arg(ap, int);
     while(--count){
       if (num != va_arg(ap, int)){
            flag = FALSE;
            break;
       }
     }
    //Step4: Now work done, we should reset pointer to NULL
    va_end(ap); 
    return flag? TRUE: FALSE;
}
int main(){
    if(isAllEqual(5, 2, 2, 2, 2, 2))
       printf(" Yes, All are equal\n");
    else
       printf(" No, All are NOT equal\n");

    if(isAllEqual(4, 2, 4, 2, 5))
       printf(" Yes, All are equal\n");
    else
       printf(" No, All are NOT equal\n");
    return 0;
}

Output: 

 Yes, All are equal
 No, All are NOT equal

Check codepade.

My boolean isAllEqual(int count, ...) function can check any number of integers, count = number of values you wants to compare. e.g. In isAllEqual(4, 2, 4, 2, 5) first 4 means you wants to compare next four values.

A short theory in four points will help you to understand my code.

Community
  • 1
  • 1
Grijesh Chauhan
  • 57,103
  • 20
  • 141
  • 208
0

I would suggest writing a macro or a function(if it is array with big size or if it is allocated at runtime) in this case.

wirm
  • 100
  • 5