基于模板字符串文字返回的C++函数指针

map<string, function<int(int)>

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

int add(int a, int b){return a+b;}
int subtract(int a, int b){return a-b;}
int multiply(int a, int b){return a*b;}
int divide(int a, int b){return (b!=0?a/b: -1);}
map<string, function<int(int,int)>> functions = 
{
    {"add",add},
    {"subtract",subtract},
    {"multiply",multiply},
    {"divide",divide}
};

int main(int argc, char** argv)
{
    cout << functions["add"](5,2);
    return 0;
}