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Subject: Re: [boost] Any interest in dynamic dispatching mechanism from " interface" to template functions ?
From: Raffi Enficiaud (raffi.enficiaud_at_[hidden])
Date: 2010-07-01 11:20:22

Mathias Gaunard <mathias.gaunard <at>> writes:

> Isn't that what apply_visitor already does, albeit it only deals with
> variant and not base classes?

Not exactly (as far as I understood apply_visitor). The dispatch
is a mapping from a call to an interface function (variant,
virtual abstract classes, etc) to the appropriate template
function doing the job.

In the example I provided, the "MyInterface const*" class
will be tested for exact matching with the template
"real_type const&", while the variants will be tested for
convertibility and "back" convertibility at the end of
the call (tell me if it is not clear :) ). Plus the
call succeeds when all the parameters have been matched.

So the first call ("template_function < class_t1 >")
succeeds if
- "i_class1" (MyInterface const *) can be dynamic_casted
to "class_t1 const&",
- "param" (variant const&) can be casted to double and
- "param_out" (int) can be casted to variant& ("out").

Otherwise the second template function
("template_function < class_t2 >") is tested.

The types which are tested for matching are either convertibles and/or exact,
depending on the convertor. Currently I have 3 different type of convertors:
- compile time: which map for instance an uint8 to a float
- dynamic_cast: from a base class to a concrete class
- runtime: depending on the content of the object (variant)

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