exercise14_44.cpp

#include <iostream>
#include <string>
#include <map> 
#include <functional> 

int add(int i, int j) { return i + j; }
auto mod = [](int i, int j) { return i % j; };
struct Div { int operator ()(int i, int j) const { return i / j; } };

auto binops = std::map<std::string, std::function<int(int, int)>>
{
	{ "+", add },                               // function pointer 
	{ "-", std::minus<int>() },                 // library functor 
	{ "/", Div() },                             // user-defined functor 
	{ "*", [](int i, int j) { return i*j; } },  // unnamed lambda 
	{ "%", mod }                                // named lambda object 
};


int main()
{
	while (std::cout << "Pls enter as: num operator num :\n", true)
	{
		int lhs, rhs; std::string op;
		std::cin >> lhs >> op >> rhs;
		std::cout << binops[op](lhs, rhs) << std::endl;
	}

	return 0;
}