C Programming

Question

P1:

int main()
{
int a,b,c;
a = 10;
a>=5? b=100 : b=200;
printf("%d %d",a,b);
    return 0;
}

P2:

int main()
{
int a,b,c;
a = 10;
a>=5? b=100 : (b=200);
printf("%d %d",a,b);
    return 0;
}

P1 gives error as

lvalue required as left operand of assignment
 a>=5? b=100 : b=200;
                ^

while P2 doesn't!

Please explain why?

Answer 1

precedence of RELATIONAL OPERATOR> TERNARY OPERATOR > ASSIGNMENT OPERATOR

therefor in our case evaluation order should be (>=) first the (?:) then (=)

according to this order of precedence ,  in P1 , expression a>=5? b=100 : b=200;  is evaluated as

((a>=5)?b=100:b)=200 which is invalid because lefthand side should be a variable to store 200 hence ur getting error of lvalue required. while this is not an issue in P2