'final' function implementations in interface definition

[Robert Clipsham]

HOSOKAWA Kenchi wrote:
> Robert Clipsham Wrote:
> 
>> If you want this then you need abstract classes. 
>> http://www.digitalmars.com/d/1.0/attribute.html#abstract
>>
>> abstract class A
>> {
>>    abstract void f(int);
>>    final void f_twice(int i) { f(i); f(i); }
>> }
>>
>> class B : A { }
>>
>> (new B).f_twice(1);
> 
> Unfortunately the derived class have already inherited another class in my code.
> I need interface inheritance.
> 

You could use a template mixin then:

template MyInterfaceMethods()
{
   final void f_twice( int i ) { f(i); f(i); }
}

interface I
{
   void f( int );
}

class A : I
{
    mixin MyInterfaceMethods;
}