#include <string>
#include <iostream>
#include <functional>
 
// remember a struct is just a class whose members are, by default public!
struct hello_message
{
   // function operator of type std::string(std::string const &) const
   std::string operator () (std::string const & name) const
   {
      return "hello, " + name;
   }
};
 
// this expects a functor to execute
void execute_functor(
   std::function<std::string (std::string)> const & functor
   )
{
   auto && msg = functor("evilrix");
   std::cout << msg << std::endl;
}
 
int main()
{
   // create the function object
   auto && hellomsg = hello_message();
 
   // pass to the executor
   execute_functor(hellomsg);
}

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