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Date: Tue, 6 Sep 2011 14:48:36 -0700
From: alfredo.correa@gmail.com
To: boostusers@googlegroups.com
Subject: [Boost-users] [type_traits][function_traits] generic way of obtaining argument of *both* a function and function object

Hi,

 Is there a uniform way to obtain the argument type of function object and of a function at the same time.

For example:

double fun(int a){ return ... ;}
struct A{
  double operator()(int a){ return ...;}
  typedef int argument_type; // or something like this (if needed)
};

template<class F> print_argument_type(F f){
   std::cout << typeid(
          argument_of<F>::type // or something like this ??
   ).name() << std::endl;
}

A a;
print_argument(fun); //should print  "int"
print_argument(a); //should print  "int"

Of course I am asking for something that at least works on objects in which operator() is not overloaded.
For functions we have function_traits< ... >::arg1_type (and other MPL variants) but I can not find a generic solution that also works for objects.

In other words I need something like boost/std::result_of but for the argument type; if this is not possible in general because of language limitations (e.g. because operator() can be overloaded) I am willing to accept any convention from out there that works both for functions and funciton objects. Just wanted to know what boost can say about this problem.

Maybe something that looks into the arguments of the member-function A::operator() via type_traits in case A is a class?

Thanks,
Alfredo


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