Get argument type of template callable object

Question

Consider the following function:

template
void register_handler( F& f ) // any callable object
{
   // find out T - the argument type of f         


        

Answer 1

if F is a std::functionyou should be able to use the its member type and check with `std::is_same':

template
void register_handler( F& f ) // any callable object
{
   // find out T - the argument type of f
   if(std::is_same::value)
   { .... }
   //etc .....

}

An up and running example here

but that kind of code can quickly become a mess to maintain.