C Programming - Control Instructions - Discussion

@Cynthia Newton

You are wrong. The given answer is correct only.

Because we can use '=' and '==' in if conditions.

Eg: The followings are valid if conditions.

1. if(0 == 0) // true
2. if(1 == 2) // false
3. if(i = 0) // false
4. if(i = 1) // true

Eg: Some invalid if conditions.

5. if(0 = 0) // Invalid. LValue required
6. if(1 = 2) // Invalid. LValue required

But, the actual reason for the error "LValue required error" is due to the following reason:

The assignment operator '=' always requires an operand immediate left.

LValue --> LEFT side operand required.

In the above 4 examples, 3 and 4 uses an operand immediate LEFT side to the '=' operator. So, it is a valid statement. But in the case 5 and 6 it fails due to 'LValue required'.

I hope this may help you. Have a nice day!

/* Note: GCC Compiler (32 Bit Linux Platform). */

Then this is also not working why?

#include<stdio.h>
int main()
{
int i = 10, j = 15, a, b;
if((a=i % 2) = (b= j % 3))
printf("IndiaBIX\n");
return 0;
}

Equality can be checked with == symbol .

The condition should be - if(i%2 == j%3) , where even then it will be a error due to the lack of value for j.

Hence it is an Expression syntax (option A).

@Navi.

It should be:

#include<stdio.h>
int main()
{
int i = 10, j = 15, a, b;
if((a=i % 2) == (b= j % 3))
printf("IndiaBIX\n");
return 0;
}

@Ravinder: In 5 and 6 there are no any identifier immediet to the left which should be mendatory to have the result of that expression.

L value always must be a variable and should not be a constant.

R value always must be a constant to assign for that variable.

@sundar,
as you mention at above explanation of if's valid condition example 4th one is false but not true..

I can't understand your explanation. Please clearly explanation. Lvalue means?

I can't understand I want clear explanation. Why we use L value.

I want to know what is Rvalue. Please explain.