Re: [Boost-users] [FunctionTypes] Testing for a general callable type.

26 Mar 2013


      2013/3/26 Jeffrey Lee Hellrung, Jr. 
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On Mon, Mar 25, 2013 at 12:22 PM, Nevin Liber wrote:
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On 22 March 2013 08:15, TONGARI  wrote:
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https://github.com/jamboree/boost.has_call
It doesn't seem to work with default arguments. :-(
Here is my test case (under gcc 4.7.2 -std=c++0x):
#include "boost/type_traits/has_call.hpp"
#include <cassert>
template
bool HasCall(F const&)
{ return boost::has_call::value; }
void DefaultVal(int = 0) {}
int main()
{
    assert(HasCall(DefaultVal));
}
That's because the type of DefaultVal is void ( int ). Function types
cannot encode the default'ness of parameters.
Yes. Instead, the following works:

    struct F
    {
        void operator()(int = 0){}
    };

    ...

    assert(HasCall(F()));