将仿函数作为函数指针传递

#include<iostream>
#include<functional>

class Multiplier {
public:
    Multiplier(int multiplier) : multiplier_(multiplier) {}

    int operator()(int value) const {
        return value * multiplier_;
    }

private:
    int multiplier_;
};

int main() {
    Multiplier multiplier(3);
    int result = multiplier(4);
    std::cout << "Result: "<< result<< std::endl;

    return 0;
}