c++ - Lambda`s internal this in c++

Question

如果 lambda 函数 ic C++ 是由仿函数实现的，为什么这是不可能的？

#include <iostream>

class A
{
public: 
    int a;  
    void f1(){ [](){std::cout << this << std::endl ;}();};
};

int main()
{
    A a;
    a.f1();
}

我收到错误 9:34: error: 'this' was not captured for this lambda function。如果我理解正确，如果 lambda 是作为仿函数类实现的，为什么无法获取它的内部 this？

编辑:仿函数类的this，而不是A类实例的this。

Answer 1

来自 lambda :

For the purpose of name lookup, determining the type and value of the this pointer and for accessing non-static class members, the body of the closure type's function call operator is considered in the context of the lambda-expression.

struct X {
    int x, y;
    int operator()(int);
    void f()
    {
        // the context of the following lambda is the member function X::f
        [=]()->int
        {
            return operator()(this->x + y); // X::operator()(this->x + (*this).y)
                                            // this has type X*
        };
    }
};

所以，不可能如你所愿地引用this。