c++ expression must be a modifiable value

Question

Problem:

I have a sample c++ code below that throws me back an error: “c++ expression must be a modifiable value” What could be the reason?

int A = 3; 
int B = 5; 
int match = 3;
for ( int k =0; k < B; k ++ )
{
    match --; 
    if ( match == 0 && k = A )
    {
         std::cout << " equals" << std::endl;
    }
}

Thanks for your help.

Answer 1

You need to remember, the assignment operator has lower precedence than &&, so your condition is comparable as:

if ((match == 0 && k) = a)

But the left-hand side of this is an rvalue, namely the boolean resulting from the evaluation of the sub­expression match == 0 && k, so you cannot assign to it.

On the contrary, the comparison has higher precedence, so match == 0 && k == a is comparable to:

if ((match == 0) && (k == a))

I hope you get the point now.