Is metaprogramming useful?

[Georg Wrede]

Don Clugston wrote:
> Georg Wrede wrote:
>> If we had Perfect Metaprogramming(TM) in D, then I could do the 
>> following:
> 
> What's wrong with
> 
> void unless(bool cond, lazy void delegate() blockstatement) {
>    if (!cond) blockstatement();
> }

What's wrong is that it's besides the point. :-)

Your solution is a good one, it works today, and looks uncomplicated. Of 
course, like you said, one has to get accustomed to a slightly unusual 
syntax. (Well, at least unusual for a simple conditional.) Which would 
of course be more hassle for the user than if(!fullMoonTonight){}, so 
the point gets lost.

But even that's beside the point. The point had already got derailed 
because I jumped to specifics too soon. ;-)

---

But it did bring up an interesting remark by Andrey about Nemerle. Got 
me thinking, some implementations of Lisp are compile-only (that is, 
they never interpret), and there probably are other compiled languages 
too (Don't know about Nemerle, gotta check it out some day), that 
support the kind of stuff that I did in the example.

So there should exist no a priori reason why it couldn't be done in D?

(Of course the mere proposition scares everybody gutless here, but I'm 
talking _technical_ reason. Compare also to my reply to Jarrett, right 
next to this post in this thread.)