mixins: Shouldn't this work?

[Daniel Keep]

mike wrote:
> Am 04.01.2007, 00:27 Uhr, schrieb Kirk McDonald  
> <kirklin.mcdonald at gmail.com>:
> 
>> Mixins are for mixing-in declarations, not statements. What you're 
>> doing  is this:
>>
>> float foo(float x, float y) {
>>      mixin trace!("foo");
>>      return x / y;
>> }
>>
>> Becomes:
>>
>> float foo(float x, float y) {
>>      void trace() {
>>          scope (failure) writefln("Trace: ", "foo");
>>      }
>>      return x / y;
>> }
>>
>> See? The "scope (failure)" is inside a nested function. It applies to  
>> the scope of that function, and doesn't help one iota. :-)
> 
> 
> Ow! I see. So no way to do that?
> 
> -mike
> 

Since you can't mixin statements, not directly.  Any way you do it, you 
would end up using a function at some point, so you may as well just do 
that, and rely on the compiler to inline the function for you.

*Actually reads code*

Ooooh, I see what you're up to.  Hmm... that is a tricky one.  You could 
try using a templated function with a delegate parameter... I have no 
idea if this actually works; perhaps a template guru could help you with 
the details :P

 > auto trace(T_Return)(char[] name, T_Return delegate() dg)
 > {
 >     debug scope(failure) writefln("Trace: %s", name);
 >     return dg();
 > }
 >
 > float foo(float x, float y)
 > {
 >     return trace!(float)("foo",
 >     {
 >         return x / y;
 >     });
 > }

NB: You might be able to remove the "!(float)" bit, I'm not sure.  I 
haven't really delved into the newer template stuff...

	-- Daniel