On 9/6/07, Dean Michael Berris <mikhailberis@gmail.com> wrote:
On 9/6/07, Mathias Gaunard <mathias.gaunard@etu.u-bordeaux1.fr> wrote:
Marco Costalba wrote:
What I would need is an implementation of the following algorithm:
foreach(f in Set) if ( "f(v1,v2,..,vk)" is compilable ) return f;
function_traits, SFINAE, and verbose meta-programming.
This would work if you were using something like Boost.Fusion in the background where most of the processing is done at compile time. However I believe the OP was looking for a solution at runtime, which pretty hard to achieve if you're going to rely on RTTI.
Yes. Correct. At compile time it's not a problem, also is not a problem to check for the same signature parameter types at runtime. The real problem is to support automatic conversions (int -> double, derived* -> base*) at runtime.
I'm looking for a similar solution, but more towards improving http://dispatcher.sourceforge.net/ to be able to support multiple function signatures in a single dispatcher instance. I think I've got a way to accomplish that with Boost.Fusion, but I doubt this same approach you propose will work for runtime determination.
Unless I'm missing something, in which case please enlighten me.
I studied your dispatcher code. The "trick" is that it supports only one signature per dispatcher. So that all the objects stored your maps could be easily derived form a base class with a given and fixed signature. When you want to store objects with different signatures in a single map you need (or at least I was not able to find something better ;-) to use a common base class with no signature information (StorableClass) and store pointers of that class, then you add signature info subclassing that class with a class templetized on a given signature (SignatureClass). So you have a possible map: map[(key1,p1) (key2,p2) (key3,p3) .... ] where pointers StorableClass *p1, *p2, *p3 are indeed pointers to objects of 3 different instances of a template<>SignatureClass So pointers can coexist together also if the objects they point have different signatures. In the "simple_factory.hpp" example, I posted in a previous thread, a dynamic_cast at runtime is used to check the signatures hidden behind p1,p2,p3 against a given one. The real problem is that two SignatureClass objects with different signatures: SignatureClass<int (int,int)> and SignatureClass<int (int,double)> HAVE DIFFERENT TYPE!!! so that a dynamic_cast is unable to discover that a set of values v1,v2 that could be used for the first one can be feed also to the second one. Hope is clear...at least a bit ;-) Thanks Marco