Test series

Question

int main()
{
     int a = 1, b = 2, c = 3;
     printf("%d", a += (a += 3, 5, a));
}

How is this evaluated ?

Comments

Yes

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@Shaik Masthan  sir but on running this code we are getting 8; then how it is undefined as here we use the comma so it will sure about the sequence and result into a = a+3 

 

please correct me

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@lakshaysaini2013

there are two + operators, due to the first + operator, from left side, it is going to undefined behavior.

Answer 1

#include <stdio.h>

int main(void) {
	int a = 1, b = 2, c = 3;
	a =a+ 3, 5, a;// Comma (separate expressions) has least precedence in C so a=1+3; so a=4
	a =a+ a; //() has highest precedence are evaluated first so 4+4 see link below
    printf("%d", a);
	return 0;
}

please check the link:https://www.geeksforgeeks.org/c-operator-precedence-associativity/ 

I hope it will clear your doubt.

Answer 2

Ok so first let me list out all operators used here..

1. ()
2. +=
3. ,

Now above operator list I wrote, it is as per C's precedence rule here

So first, it let's take () part,

(a+=3,5,a) =>  As we know, comma proceeds in left-to-right, so this is equal to (a=4,5,a),

Now from above we can say a is having value 4 and we have used parenthesis here, it will take last value which is not but a so finally

     a+= a

=> a+=4

=> a=a+4

and we know a=4 hence

=>a = 4+4=8

so answer is 8.