In C and C++, comma is the last operator in precedence table. So comma should be carefully used on right side of an assignment expression. For example, one might expect the output as b = 10 in below program. But program prints b = 20 as assignment has higher precedence over comma and the statement “b = 20, a” becomes equivalent to “(b = 20), a”.
#include<stdio.h> int main()
{ int a = 10, b;
b = 20, a; // b = 20
printf ( " b = %d " , b);
getchar ();
return 0;
} |
Putting a bracket with comma makes b = a (or 10).
#include<stdio.h> int main()
{ int a = 10, b;
b = (20, a); // b = a
printf ( " b = %d " , b);
getchar ();
return 0;
} |
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