mixin troubles

[Josh Stern]

On Fri, 06 Oct 2006 09:04:05 +1000, Derek Parnell wrote:

> On Thu, 05 Oct 2006 14:28:01 -0500, Josh Stern wrote:
> 
>> I think the double use of "Foo" for the template namespace and the
>> function itself made the example confusing.  The following works
>> and makes the role of the template and the function and/or class
>> names clearer (no alias really needed):
> 
> I think you have missed my point.
> 
> I want to mixin the template multiple times, each time giving the resulting
> statement a different identifier so it can be used in a simple manner. 

Yes, I missed the point that the special difficulty being addressed was
trying to avoid a name clash caused by multiple definitions.  But even so,
mixins and template seem to interact in the way I would expect and I don't
see that alias's are really required.   You have two good choices here -
either use the 'x' and 'y' extra level of namespace idea... 



import std.stdio;

template FFoo(alias b) {
  typeof(b) foo() { return b; } // foo function
 }
 void main() {
  int a=5;
  double b = 3.14;
  // FIRST TIME
  mixin .FFoo!(a) x;  // bring in the statement in the 'x' sub-namespace

 writefln(x.foo());
	 
  // SECOND TIME
  mixin .FFoo!(b) y;  // bring it in in the 'y' sub-namespace.

writefln(y.foo());
 }


...or just use an extra
level of braces around each distinct instantiation...

{
//First time
mixin .FFoo!(a);  

}

{
// Second time	 
 mixin .FFoo!(b);
 writefln( foo());
}



> For
> example, using your 'different' name idea ...
> 
>  import std.stdio;
>  template FFoo(alias b) {
>   typeof(b) foo() { return b; } // foo function
>  }
>  void main() {
>   int a=5;
>   double b = 3.14;
>   // FIRST TIME
>   mixin .FFoo!(a) x;  // bring in the statement calling it 'x' writefln(
>   x() );
>   // SECONND TIME
>   mixin .FFoo!(b) y;  // bring it in again but call it 'y' this time.
>   writefln( y() );
>  }
>  }
>  }
> This still fails and yet looks intuitive (to me at least).

I  think of mixin as a smart replacement for macros so I wouldn't expect
the above to work.