testing if an instance is a subclass of a given class

[downs]

Paul Dufresne wrote:
> And would it be possible to write an isSubclass function in D based on this test...
> I don't see how I would pass the Class for the test... what come in mind naturally would be:
> bool isSubclass (Class C, Object o){
>   if (cast (C o) then return true else return false;
> }
> 
> but the Class type does probably not exist ... does it?

Close.

bool isA(T)(Object obj) {
  return (cast(T) obj)?true:false;
}

..

class A { }
class B : A { }

A x = new B;

if (isA!(B)(x)) { } else { }

Note however, that this is an exercise in redundancy, as it is almost exactly the same as "if (cast(B) x)".

I really recommend you use that instead.