Imcompatible type, const and const

[bearophile]

Duarte:

> What am I missing here? The same code in C++ compile, so I was 
> assuming it would just as well compile in D.

C++ and D are two different languages, and among other things 
they have two very different constant-ness systems, so code in 
one language often can't work in the other.

In your code probably there are multiple problems. One problem I 
see is here:

     Vector2 opBinary(string op)(const Point2 _right) {
         static if(op == "-") {
             return new Vector2(this.x - _right.x, this.y - 
_right.y);
         }
     }

You have to use a template constraint otherwise one of your code 
paths returns nothing, and this is (thankfully) an error in D.

Also regarding your style, in D functions start with a lower case 
letter.

I suggest to ask similar questions in the D.learn newsgroup.

Bye,
bearophile