On Sat, May 10, 2008 at 10:43 AM, vicente.botet <vicente.botet@wanadoo.fr> wrote:
Try with struct foo_t { template<class T> void operator()(T){} } foo;
boost::function<void(int)> f = foo; // ok it works, no ambiguity, object is instantiated as foo_t::operator<int>() boost::multi_signature_function:: function<boost::mpl::vector<void(int), void(std::string)> > msf = foo; // error! Ambiguous call <strip> could be void(int) or <strip> void(std::string) msf = f; // this works! no more ambiguity, foo_t is instantiated with T = int So the bottom line is that it does not work because compiler does not know to which internal boost::function to bound foo, because it could be bounded to both boost::function<void(int)> and boost::function<void(std::string)> an "ambiguous call" type error arise...as it should, if I can dare. Replying to a previous message...
This library extension, although flexible and IMHO powerful is notably very simple and small, so I would like to ask if someone is interested to add this code in some way directly to boost.function
While useful, I do not think this library belongs in boost function (which is monomorphic), but it should be a library of its own.
Form boost.function documentation: "Generally, any place in which a function pointer would be used to defer a call or make a callback, Boost.Function can be used instead" Where boost.function naturally models a function, multi-signature boost::function naturally models an overload set In the examples there is the implementation of an object factory that comes out nice and small using MSF. Why? Essentially it boils down to the fact that class constructors are an overload set! I can use boost::function to bound to an object member function, say foo, but if there exist more then one member named foo and I want to bound them all I have to use different named boost::functions, this is not a natural extension. With MSF I model naturally this case because with a single named MSF object I model all the single named foo members of my object. So the bottom line here is: "Where boost.function naturally models a function, multi-signature boost.function naturally models a set of same named functions" Thanks Marco