[C++知识库]c++ lambda的按值访问和按引用访问

$ cat test2.cpp
#include <iostream>


using namespace std;

void lambda_test(void)
{
    int x = 2;
    int y = 10;

    auto lambda = [x, &y] {    //此处x = 2，会影响测试1和测试2中的x。
        cout << "x: " << x << endl;
        cout << "y: " << y << endl;
        ++y;
    };


    lambda();   //测试1
    cout << "x: " << x << endl;
    cout << "y: " << y << endl;

    cout << "x = y = 77" << endl;
    x = y = 77;  //测试2

    lambda();
    cout << "x: " << x << endl;
    cout << "y: " << y << endl;
}


int main(int argc, char *const argv[])
{
    lambda_test();
    return 0;
}

编译：

$ g++ -std=c++11 test2.cpp

测试：

$ ./a.out
x: 2        //x = 2
y: 10
x: 2        //x = 2
y: 11
x = y = 77
x: 2        //x = 2
y: 77
x: 77
y: 78