December 06, 2012
Greetings,

Given the following code:

struct Inner {

  void fun1() {}
  void fun2( string toto ) {}
  string fun3() { return "tata"; }
  string fun4( string tutu ) { return "this is going too far"; }

  void fun5( string ohOh )() {}

}

struct Outer {
  private Inner _inner;

  auto opDispatch( string method, T... )( T args ) {
    return mixin( "_inner." ~ method )( args );
  }

}

void main( string[] args ) {
  Outer outer;
  outer.fun1();
  outer.fun2( "some string" );
  auto zeString = outer.fun3();
  auto zeOtherString = outer.fun4( zeString );
  outer.fun5!"popo"(); //No compilo amigo

}

Is it possible/desirable to ever get opDispatch to delegate to a template member function?

Thanks
December 06, 2012
I mean automatically dispatch to template members, not doing it in a case by case fashion (using template if clauses for example).

Thanks
December 06, 2012
On Thursday, 6 December 2012 at 21:49:21 UTC, Phil Lavoie wrote:
> I mean automatically dispatch to template members, not doing it in a case by case fashion (using template if clauses for example).
>
> Thanks

This is a known issue of the current design of opDispatch.
December 06, 2012
Got it!
Thanks
December 07, 2012
Note that, std.typecons.Proxy implements such template member function
forwarding by opDispatch nesting.
If curious, you can look its implementation.

Kenji Hara

2012/12/7 deadalnix <deadalnix@gmail.com>

> On Thursday, 6 December 2012 at 21:49:21 UTC, Phil Lavoie wrote:
>
>> I mean automatically dispatch to template members, not doing it in a case by case fashion (using template if clauses for example).
>>
>> Thanks
>>
>
> This is a known issue of the current design of opDispatch.
>


December 07, 2012
On 2012-12-06 22:49, Phil Lavoie wrote:
> I mean automatically dispatch to template members, not doing it in a
> case by case fashion (using template if clauses for example).
>
> Thanks

As Kenji said, doing something like this:

struct Outer {
  private Inner _inner;

  template opDispatch( string method ) {
    auto opDispatch (T... ) (T args)
      return mixin( "_inner." ~ method )( args );
    }
  }
}

-- 
/Jacob Carlborg
December 07, 2012
Hi,

Indeed as he suggested. I tried to reply that I was looking at the code yesterday and that it was what I was looking for, but my post did not get through for some reasons.

Thanks!

On Friday, 7 December 2012 at 07:57:09 UTC, Jacob Carlborg wrote:
> On 2012-12-06 22:49, Phil Lavoie wrote:
>> I mean automatically dispatch to template members, not doing it in a
>> case by case fashion (using template if clauses for example).
>>
>> Thanks
>
> As Kenji said, doing something like this:
>
> struct Outer {
>   private Inner _inner;
>
>   template opDispatch( string method ) {
>     auto opDispatch (T... ) (T args)
>       return mixin( "_inner." ~ method )( args );
>     }
>   }
> }

December 07, 2012
Hi,

Yes indeed Kenji pointed me in the right direction. I tried posting that I looked at the code he suggested and found what I was looking for, but I had some issue posting :(.

Thanks



On Friday, 7 December 2012 at 07:57:09 UTC, Jacob Carlborg wrote:
> On 2012-12-06 22:49, Phil Lavoie wrote:
>> I mean automatically dispatch to template members, not doing it in a
>> case by case fashion (using template if clauses for example).
>>
>> Thanks
>
> As Kenji said, doing something like this:
>
> struct Outer {
>   private Inner _inner;
>
>   template opDispatch( string method ) {
>     auto opDispatch (T... ) (T args)
>       return mixin( "_inner." ~ method )( args );
>     }
>   }
> }

December 09, 2012
On Thursday, 6 December 2012 at 23:01:19 UTC, deadalnix wrote:
> On Thursday, 6 December 2012 at 21:49:21 UTC, Phil Lavoie wrote:
>> I mean automatically dispatch to template members, not doing it in a case by case fashion (using template if clauses for example).
>>
>> Thanks
>
> This is a known issue of the current design of opDispatch.

 It seems like there should be a way to separate template function calls to opDispatch and keep opDispatch's own template half separate. Hmmm... Some type of separator.

 It would likely have to allow a beginning tuple, as well as call opDispatch that would recognize it as such.

 In theory...

 auto opDispatch(T..., string method, V...)(V args)

 Assuming it would be allowed, T represents the template portion of a call. Since the ... makes it illegal to be first (in normal cases) it may allow a special rule in order to understand it's a passable tuple for templates only, and allowed for only the first and last arguments. Or would T[] be better?

 Then calling such an opDispatch may be...
 {
    static assert (!T.length) {
      return mixin("._inner." ~ method)(args);
    } else {
      return mixin("._inner." ~ method)!(T)(args);
    }
 }

 The rewrite of such a function call would be..

  auto zeOtherString = outer.fun4( zeString );
  outer.fun5!"popo"(); //No compilo amigo

  would become (I think?)

  //depending on how they do it...
  auto zeOtherString = outer.opDispatch("fun4")(zeString);
  auto zeOtherString = outer.opDispatch([], "fun4")(zeString);
  auto zeOtherString = outer.opDispatch(void[0], "fun4")(zeString);
  outer.opDispatch(["popo"], "fun5")();

 Having the passable tuple after the method may be confusing, but might equally work...

  auto opDispatch(string method, T t, V...)(V args)   (or is it 'T[] t'?)

 Allowing a blank (for t) wouldn't probably be allowed, so two opDispatches might have to be made, but that might be minor. Depends on what makes sense and how walter/andrei decide to handle if (if at all).

 If it still requires a separating type, you could always use void...

  auto opDispatch(T[], void, string method, V...)(V args)
  outer.opDispatch(["popo"], void, "fun5")();

 or??

  auto opDispatch(string method, T[], void, V...)(V args)

  //void and non-void attempted? Or always insert void silently?
  outer.opDispatch("fun5", ["popo"])();
  outer.opDispatch("fun5", ["popo"], void)();
December 10, 2012
On Sunday, 9 December 2012 at 03:33:07 UTC, Era Scarecrow wrote:
> On Thursday, 6 December 2012 at 23:01:19 UTC, deadalnix wrote:
>> On Thursday, 6 December 2012 at 21:49:21 UTC, Phil Lavoie wrote:
>>> I mean automatically dispatch to template members, not doing it in a case by case fashion (using template if clauses for example).
>>>
>>> Thanks
>>
>> This is a known issue of the current design of opDispatch.
>
>  It seems like there should be a way to separate template function calls to opDispatch and keep opDispatch's own template half separate. Hmmm... Some type of separator.
>

It seems that using opDispatch within opDispatch as shown before in the thread solve the problem. This technique should be advertised.
Top | Discussion index | About this forum | D home