c++学习2

#include <iostream>
#include <iomanip>
using namespace std;

class Base {
public:
    virtual void f() { cout << "base" << endl; }
};
class Derived : public Base{
public:
    void f() { cout << "derived" << endl; }
};
class Base2 {
public:
    virtual void g() { cout << "base2 process g" << endl; } // dynamic_cast only work under polymorphic settings
};
class Derived2 : public Base2{
public:
    void f() { cout << "derived2" << endl; }
};

int main() {
    /*
    Base *b = new Derived;
    b->f(); //base

    Base *b = new Derived;
    Derived *a = static_cast<Derived *>(b);
    a->f(); //derived

    Base *b = new Derived;
    b->f(); //derived, derived overwrite base in virtual table
    Derived *a = dynamic_cast<Derived *>(b);
    a->f(); //derived, same with b->f()
 */
    Base2 *b = new Derived2;
    //b->f(); // compile error
    Derived2 *a = dynamic_cast<Derived2 *>(b);
    a->f(); //derived2, same with b->f()
    return 0;
}

auto f = [](int a, int b){return a + b;};
cout << f(1,2) << endl; //3
cout << [](int a, int b){return a + b;}(1,2) << endl; //3
int a = 0; int b = 0; int c = 0;

//cout << [=](int a, int b){c = 1; return a + b;}(1,2) << "\t" << c << endl;
// error: cannot assign to a variable captured by copy in a non-mutable lambda
//cout << [](int a, int b){int c = 1; return a + b;}(1,2) << "\t" << c << a << endl; //3 \t 0

cout << [&](int a, int b){c = 1; return a + b;}(1,2) << "\t" << c << "\t" << a << endl; //3 \t 1
cout << [&c](int a, int b){c = 1; return a + b;}(1,2) << "\t" << c << endl; //3 \t 1