[D.typesystem] Suggestion for improving OO inheritance models

[Jacob Carlborg]

On 2010-09-01 23:39, Andrej Mitrovic wrote:
> You mean like this?:
> module add_virtual_functions;
>
> import std.stdio : writeln;
>
> void main()
> {
>      test();
> }
>
> mixin template Foo()
> {
>      void func()
>      {
>          writeln("Foo.func()");
>      }
> }
>
> class Bar
> {
>      void func()
>      {
>          writeln("Bar.func()");
>      }
> }
>
> class Code : Bar
> {
>      mixin Foo;
> }
>
> void test()
> {
>      Bar b = new Bar();
>      b.func();   // calls Bar.func()
>
>      Code c = new Code();
>      c.func();   // calls Code.func()
> }
>

No, that is overriding. Overloading is having several methods with the 
same name taking different number of parameters or parameters of 
different types.

module test;

mixin template Foo ()
{
	void bar (int i) {};
}

class Bar
{
	void bar () {};
	mixin Foo;
}

void main ()
{
	auto bar = new Bar;
	bar.bar(4); // line 17
	bar.bar();
}

The above code results in these errors:

test.d(17): Error: function test.Bar.bar () is not callable using 
argument types (int)
test.d(17): Error: expected 0 arguments, not 1 for non-variadic function 
type void()


> On Wed, Sep 1, 2010 at 11:30 PM, Jacob Carlborg<doob at me.com>  wrote:
>> On 2010-09-01 22:44, Philippe Sigaud wrote:
>>>
>>> On Wed, Sep 1, 2010 at 18:13, retard<re at tard.com.invalid>  wrote:
>>>
>>>
>>>     Have you taken a loot at Scala&  traits already? It would be a great
>>>     starting point.
>>>
>>>
>>> Scala's traits are great! Implicits in Scala are quite interesting too.
>>> Also, Haskell typeclasses
>>>
>>> I wonder if D can have part of Scala traits functionality with mixins?
>>
>> You can't use D template mixins to add methods that will overload existing
>> methods.
>>
>>
>> --
>> /Jacob Carlborg
>>


-- 
/Jacob Carlborg