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

This is because everything else follows the practice of declaring variables before you use them, eg:

public static void main(String[] args){ 
  // scope of args
}

for(int i=1; i<10; i++){
  // scope of i
}


{
...
int somevar;
//begin scope of var

...

//end of scope of var
}

This is because things are parsed top down, and because following this convention keeps things intuitive, thus why you can declare a while(int var < 10) because the scope of that var will be the area inside the loop, after the declaration.

The do while doesn't make any sense to declare a variable because the scope would end at the same time it would be checked because that's when that block is finished.