March 11, 2008
With struct inheritance I mean the following and not the "concept interfaces".

struct Base
{
  void doStuff()
  {
  }
}

struct Derived
{
  inherit Base base;
}


  Derived d;
  d.doStuff();


Sort of like having a compile time inheritance, with its limitations.
March 11, 2008
Sclytrack schrieb:
> Sort of like having a compile time inheritance, with its limitations.

See also this thread
http://www.digitalmars.com/webnews/newsgroups.php?art_group=digitalmars.D&article_id=64764
March 11, 2008
Forget what I said, I see that there is already something specified in the "WalterAndrei.pdf". Something called "alias this" and I forgot about it.

"allows importing the fields of a member into the namespacece of a struct."

	struct M {int a; }
	struct S {
		M m;
		alias m this;
		int b;
	}

	S s;
	b.a;
	s.b;

Wonder if it works with member functions too.
March 11, 2008
On Tue, 11 Mar 2008 14:02:26 +0300, Sclytrack <Sclytrack@pi.be> wrote:

> Forget what I said, I see that there is already something specified in the
> "WalterAndrei.pdf". Something called "alias this" and I forgot about it.
>
> "allows importing the fields of a member into the namespacece of a struct."
>
> 	struct M {int a; }
> 	struct S {
> 		M m;
> 		alias m this;
> 		int b;
> 	}
>
> 	S s;
> 	b.a;
> 	s.b;
>
> Wonder if it works with member functions too.

As of now, it's not implemented.

Your best best whould be to use mixins, and it's almost 100% same syntax:

template Base()
{
    void doStuff()
    {
    }
}

struct Derived
{
    mixin Base;
}

as opposed to:

struct Base
{
  void doStuff()
  {
  }
}

struct Derived
{
  inherit Base base;
}

However, you still can't cast Derived to Base. And proposed syntax (one with aliased this) most probably won't too (at least, S doesn't look like it inherits M).

I still think that structs should just support inheritance, maintaining the limitation of not having virtual functions. Classes could also benefit from deriving from structs, although this most probably won't ever happen, since classes are reference types and most importantly contain _vtptr as a first member and therefore no casting is possible between them.
March 11, 2008
Sclytrack wrote:
> With struct inheritance I mean the following and not the "concept interfaces".

If you're going to have any syntax for it, why not use the same syntax that you get with classes?

You'd have no polymorphism; the only benefits would be transparent aggregation and maybe `is (DerivedStruct : BaseStruct)` would return true.

However, you can get automatic aggregation with some (perhaps slightly tedious) template magic. I'm not interested in writing it, though, because it's tedious and fulfills no need for me.
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