Re: [boost] [challenge: Dynamic Overloads] [was Dynamic Overloads and was Re: Runtime Dynamic Dispatch Library (0.2)]

From: Marco (mrcekets_at_[hidden])
Date: 2007-10-08 05:11:36

On Mon, 08 Oct 2007 07:39:22 +0200, Marco Costalba <mcostalba_at_[hidden]>  
wrote:

> On 10/8/07, Joel de Guzman <joel_at_[hidden]> wrote:
>> There's no way to detect the signature
>> of a template function (the operator()):
>>
>
> Perhaps you don't need this. You only need to check if the template
> function operator() matches one signature in the Signatures set.
>
> I have found this nice (and very small) code from Paul Mensonides that
> seems to works (at least for me)
>
> http://www.mail-archive.com/[e-mail]/msg00164.html
>
> The limitation is that you have to specify the type of the function,
> but in our case is not a problem because we have a finite set called
> 'Signatures' among which to choose the operator() type.
>
> As you can see from his testing example:
>
> truct X {
>     void operator()(void) {
>         return;
>     }
> };
>
> struct Y { };
>
> struct Z {
>     template<class T> T operator()(T v) const {
>         return v;
>     }
> };
>
> int main(void) {
>     std::cout
>         << has_function_call<void (X::*)(void)>::value << '\n'
>         << has_function_call<void (Y::*)(void)>::value << '\n'
>         << has_function_call<int (Z::*)(int) const>::value << '\n';
>     return 0;
> }
>
> It is possible to check against any operator() given that you now the
> signatures you are looking for. Now the challange is, given a function
> obect of class F, to forge a way to loop across Signatures, that are
> function signatures,
>
> void (void)
> void (void)
> int (int) const
>
> transform in the corresponding member signatures of class F
>
> void (F::*)(void)
> void (F::*)(void)
> int (F::*)(int) const
>
> And check  each one with has_function_call() until a match is found or
> return an error otherwise.
>
> Easier to say then to do ;-)
>
> Marco

This is exactly how my second implementation works. :-)
See my proposal:
http://archives.free.net.ph/message/20071007.223315.b8f57ef5.en.html

Regards,
Marco

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