C++primer5th课后题14.44，二元处理运算

习题14.44 简单桌面计算器，处理二元运算

map<string, function<int (int, int)>> binOps = {    {"+",plus<int>()},//标准库函数对象    {"-",minus<int>()},    {"*",multiplies<int>()},    {"/",divides<int>()},    {"%",modulus<int>()}};int main(){    int a, b;    string op;    cin >> a >> op >> b;    cout << binOps[op](a, b) << endl;}