c++ lambda函数的真实面目

#include <functional>
#include <iostream>
//基础函数
void printInfo(int a, int b, int c) {
            std::cout << " a " << a << " b " << b << " c " << c << std::endl;
}

//操作符重载函数
struct Print {
    void operator() (int a, int b, int c) const {
            std::cout << " a " << a << " b " << b << " c " << c << std::endl;
    }
};
//模板函数
template<typename T1, typename T2, typename T3>
void templatePrint(T1 a, T2 b, T3 c) {
            std::cout << " a " << a << " b " << b << " c " << c << std::endl;
}

//操作符重载 + 模板 的函数
struct TemplatePrint {
    template<typename T1, typename T2, typename T3>
        void operator() (T1 a, T2 b, T3 c) const {
            std::cout << " a " << a << " b " << b << " c " << c << std::endl;
    }
};

inline void print(int a, int b, int c) {
    std::cout << " a " << a << " b " << b << " c " << c << std::endl;
}
template<typename Fun>
void printUseFun(Fun fun, int a, int b, int c) {
    fun(a, b, c);
}
void test_1() {
    Print printUseClass;    
    TemplatePrint printUseTempClass;

    printInfo(1, 2, 3);
    printUseClass(1, 2, 3); //operator() (int a, int b, int c)

    templatePrint(1, 2, 3); 
    printUseTempClass(1, 2, 3);
    print(1, 2, 3);

    //以前inline 函数跟普通函数调用差不多
    //lambda就是个inline函数, 只是把 inline 函数作为一个参数或者一个local变量来使用, 

    std::cout << "lamda: " << std::endl;
    auto local = [](int a, int b, int c) {
        std::cout << " a " << a << " b " << b << " c " << c << std::endl;
    };
    printUseFun(local, 1, 2, 3);
    printUseFun([](int a, int b, int c) {
        std::cout << "lamda2:" << std::endl;    
        std::cout << " a = " << a << " b = " << b << " c = " << c << std::endl;
    }, 2, 3, 5);

    int a = 6, b = 7, c = 8;

    auto local2  = [a, b, c]() {
        std::cout << " a = " << a << " b = " << b << " c = " << c << std::endl;
    };
    local2();

    auto local3 = [=]() {
        std::cout << "====" << std::endl;
        std::cout << " a = " << a << " b = " << b << " c = " << c << std::endl;
    };
    local3();

    auto local4 = [=]() mutable {
        std::cout << "====" << std::endl;
        a = 4, b = 4 , c = 4;
        std::cout << " a = " << a << " b = " << b << " c = " << c << std::endl;
    };
    local4();

}
int main(void) {
    test_1();
    return 0;
}