object - interface compatibility

[Walter Bright]

Frank Benoit (keinfarbton) wrote:
> 1.) Is this reference manipulation really absolutely necessary? Why?

There are two ways to implement interfaces. One is where the 
determination of what functions to call is done by repeated testing of 
an object to see what interfaces it supports. This is slow. The other 
way is to do it like C++ does multiple inheritance. Interfaces are 
really "multiple inheritance lite", and D does it the C++ way, which is 
very efficient at runtime.

> 2.) Isn't there a way to make class and iface really compatible?

Consider a function that takes an interface as an argument. Two 
different objects, A and B, can implement that interface. How can the 
function tell that it can call A.foo() when it gets an interface derived 
from A, when B doesn't have a .foo()?

> 3.) Please document this very cleanly in the D spec.