Is there a way to define variables of two different types in a for loop initializer?

Question

You can define 2 variables of the same type in a for loop:

int main() {
  for (int i = 0, j = 0; i < 10; i += 1, j = 2*i) {
    cout << j << e         


        

Answer 1

If you're having trouble with macros, there's a standard do..while trick that works perfectly:

#define MYFOR(init, test, post, body) \
    do \
    { \
        init \
        for( ; test; post) \
            body \
    } while(0)

Use it as follows:

MYFOR( int i = 0; float j = 0.0f; , i < 10 , (i += 1, j = 2.0f * i),
    {
         cout << j << endl;
    } );

It's ugly, but it does what you want: the scope of i and j is limited by the do..while loop from the macro, and it requires a semicolon at the end, so you won't get bitten by putting it in the predicate of an if/else statement.