Walter wrote:
> "Tony" <talktotony@email.com> wrote in message
> news:c89gd4$19nf$1@digitaldaemon.com...
> 
>>The mixin example overrides the definition of "x" within the function
>>"test()".
>>
>>Doesn't this violate the D rule that a symbol can't be multiply defined
>>within a function?
> 
> That rule is probably going to have to go away :-(

Looks very promising, but it could also cause quite a bit of unexpected behavior as the implementation details of a mixin can affect the calling function.  I don't suppose there are scope resolution operators to allow the caller to specify which instance of x he wants to access?

Sean

Sean Kelly wrote:
>
> Looks very promising, but it could also cause quite a bit of unexpected behavior as the implementation details of a mixin can affect the calling function.

I take it back.  The variable overriding feature pretty much takes care of this.

Sean

Great work! Apart from my comments about the general problem that the untyped compile-time language of D will probably prove to be extremely hard to debug, I really like this absolutely powerful concept of mixins.

Anybody who knows Sather will realize, that mixins contain the complete concept of implementation inheritance!

To those unfamiliar with Sather: in that highly interesting language, inheritance is completely split up into interface inheritance and implementation inheritance. Interface inheritance is just what we have in D already. Implementation inheritance is just that kind of parameterized cut-and-paste operation that mixins allow. Taking both together, it becomes obvious, that direkt inheritance is not necessary at all any more!

All the problems of multiple-inheritance in C++ come from binding together the inheritance of the class interface and the implementation of its routines. As you can easily see in D: neither interfaces nor mixins have problems with multiple inheritance (resp. inclusion of several mixins into one class definition)

Conclusion: multiple interface inheritance and mixins taken together are a complete replacement for the multiple inheritace that was dropped!

This is a great feature for D.

Coming from an enterprise software background, I can tell you that it may have a lot of use for cross-cutting concerns.  OOP generally puts tight coupling between a system-level concern and the business logic of an application, but with mixins, you could theoretically define a solution to a problem and apply it generically across business classes.  I'll play more and hopefully post something demonstrating some aspect-oriented programming techniques with D and mixins.

"Walter" <newshound@digitalmars.com> wrote in message news:c876sh$10r7$1@digitaldaemon.com...
> I have this mostly implemented. It's been based on a lot of your suggestions. The way I did it is, I think, pretty unexplored territory.
That
> means there may be some pretty cool uses for it I've never thought of. Let me know what you think, and if I missed the boat completely <g>.
>
> www.digitalmars.com/d/mixin.html
>
>

Greg Vanore wrote:
> 
> Coming from an enterprise software background, I can tell you that it may
> have a lot of use for cross-cutting concerns.  OOP generally puts tight
> coupling between a system-level concern and the business logic of an
> application, but with mixins, you could theoretically define a solution to a
> problem and apply it generically across business classes.  I'll play more
> and hopefully post something demonstrating some aspect-oriented programming
> techniques with D and mixins.

Excellent point.  This may make implementing Aspect Oriented Programming in D fairly easy, which is a technique that IMO has tremendous potential.

Sean

I do a lot of GUI programming (in C++ mostly, a little C#) and the first use that comes to mind for mixins is doing data validation... no code at hand, sorry, but think of doing an IntValidator, DoubleValidator, RangeValidator mixins (which would work kinda like MFC's DDX_Validate) and so on, and just mix 'em into your form class appropriately for each control you'd like to validate...

> > Walter wrote:
> >
> > > I have this mostly implemented. It's been based on a lot of your suggestions. The way I did it is, I think, pretty unexplored
territory.
> That
> > > means there may be some pretty cool uses for it I've never thought of.
> Let
> > > me know what you think, and if I missed the boat completely <g>.
> > >
> > > www.digitalmars.com/d/mixin.html
> > >
> > >
> >
> > Oh yeah, forgot to mention: THANKS very much for implementing this! I think this is a kick-ass feature!
>
> You're welcome! Now, I want to see a kick-ass use for this, so I can write
a
> magazine article about it! A use that is cool, not easilly expressed in other languages, and so would highlight the capabilities of D.

"Walter" <newshound@digitalmars.com> wrote in message news:c889f4$2io2$1@digitaldaemon.com...
>
> "Hauke Duden" <H.NS.Duden@gmx.net> wrote in message news:c87go0$1f8j$2@digitaldaemon.com...
> > Walter wrote:
> >
> > > I have this mostly implemented. It's been based on a lot of your suggestions. The way I did it is, I think, pretty unexplored territory.
> That
> > > means there may be some pretty cool uses for it I've never thought of.
> Let
> > > me know what you think, and if I missed the boat completely <g>.
> > >
> > > www.digitalmars.com/d/mixin.html
> > >
> > >
> >
> > Oh yeah, forgot to mention: THANKS very much for implementing this! I think this is a kick-ass feature!
>
> You're welcome! Now, I want to see a kick-ass use for this, so I can write a magazine article about it! A use that is cool, not easilly expressed in other languages, and so would highlight the capabilities of D.

I've got one of those - and the article half planned - as soon as I have an implementation that works. ;)