Question

For example, suppose we have two functions:

void sum(int x, int y)
{
   return x+y;
}

void minus(int x, int y)
{
   return x-y;
}

Is there a way to make a single function that does a sum or minus (or various other things) depending on which you want to use (perhaps by a keyword of some sort) without having to write separate functions explicitly?

Answer 1

Some one kind of beat me to this with the comments below the question, but here ya go!

#include <functional>
#include <iostream>
#include <unordered_map>

std::unordered_map<std::string, std::function<int(int,int)>> operations =
{
  { "plus",   std::plus<int>()  },
  { "minus",  std::minus<int>() }
  // etc etc
};

int main(int argc, char** argv)
{
  std::cout << operations["plus"](1, 2) << std::endl;
  std::cout << operations["minus"](2, 1) << std::endl;

}