if(a,b,x,y)

[Sky High]

can somebody explain the working of the following C code?

#include<stdio.h>
void main()
{
  int a=0, b=20;
  char x=1, y=10;
  if(a,b,x,y)
    printf("bye");
  else
    printf("BYE");
}

Output:
bye

[sicarie]

can somebody explain the working of the following C code?

#include<stdio.h>
void main()
{
  int a=0, b=20;
  char x=1, y=10;
  if(a,b,x,y)
    printf("bye");
  else
    printf("BYE");
}

Output:
bye

Somebody was coding after hitting the bar?

Whoops, wrong type of explanation. All I can do is venture a guess, so here it is:

C/C++ compilers see anything that isn't 0 as true, so the latter values overrode the 'a' in the 'if' statement, and put non-zero values in there, which the compiler then read as 'true'. But that's just my guess.

[Ganon11]

It appears that the commas are acting as or statements - in other words, the "if (a,b,x,y)" is operating like "if (a || b || x || y)". Since C/C++ interpret true/false as nonzero and zero respectively, a is the only 'false' value - thus, the if statement evaluates to true and prints "bye".

[Ganon11]

Nevermind, sicarie is right. The latter variables must be overriding the former, so in if (a, b, x, y) only y is being checked.

[Sky High]

Nevermind, sicarie is right. The latter variables must be overriding the former, so in if (a, b, x, y) only y is being checked.

thanku so much.. indeed the last expression overrides all the other expressions in if statement..

[Banfa]

OK folks the important thing here is that , is an operator (like + - [] == to name a few others). The value of the comma operator is the right hand expression, however you need to be careful because the comma operator has the lowest precedence of all operators so in this code

int a;
int b = 10;
int c = 20;
 
a = b, c;
 

a ends with a value of 10 (from b) but the value of the entire expression is 20 (from c) because due to operator precedence it is interpreted as

(a = b), c;
 

Generally speaking I think that unless you are trying to obsfucate your code the comma operator is best avoided.

[sicarie]

OK folks the important thing here is that , is an operator (like + - [] == to name a few others). The value of the comma operator is the right hand expression, however you need to be careful because the comma operator has the lowest precedence of all operators so in this code

int a;
int b = 10;
int c = 20;
 
a = b, c;
 

a ends with a value of 10 (from b) but the value of the entire expression is 20 (from c) because due to operator precedence it is interpreted as

(a = b), c;
 

Generally speaking I think that unless you are trying to obsfucate your code the comma operator is best avoided.

That makes much more sense - thanks Banfa.

(I knew the person who wrote that had been to the bar....)