13-13.md

#include <iostream>
using std::cin; using std::cout; using std::endl; using std::cerr;
#include <string>
using std::string;
#include <vector>
using std::vector;
#include <memory>
using std::shared_ptr;

struct X{
    X() {cout << "X()" << endl;}
    X(const X&){cout << "X(const X&)" << endl;}
    X &operator=(const X&);
    ~X(){cout << "~X()" << endl;}
    string a = "test";
    int b = 1;
};

X &
X::operator=(const X &x) {
    a = x.a;
    b = x.b;
    return *this;
}

//作为引用和非引用参数传递
void sumXb(X x, X &y){
    cout << x.b + y.b << endl;
}

int main() {
    X i, j;
    shared_ptr<vector<X>> spvX;
    sumXb(i, j);
    auto *px = new X();
    for (int k = 0; k != 10; ++k)
        spvX->push_back(X());
    delete px;
}