Why can't you declare a variable inside the expression portion of a do while loop?

Question

The following syntax is valid:

while (int i = get_data())
{
}

But the following is not:

do
{
} while (int i = get_data());
         


        

Answer 1

It would be very unnatural to have a declaration of i after the block and to then be able to access it in the block. Declaration in for and while are nice short-hands that give limited-scope use to a variable that is needed in the loop logic.

Cleaner to do it this way:

int i;
do {
  i = get_data();
  // whatever you want to do with i;
} while (i != 0);