13.6.2

来源：互联网发布：数据保护包括编辑：程序博客网时间：2024/06/05 17:44

13.49

StrVec(StrVec&&) NOEXCEPT;StrVec& operator=(StrVec&&) noexcept;StrVec::StrVec(StrVec &&s) noexcept : elements(s.elements), first_free(s.first_free), cap(s.cap){    s.elements = s.first_free = s.cap = nullptr;}StrVec& StrVec::operator = (StrVec &&rhs) noexcept{    if (this != &rhs) {        free();        elements = rhs.elements;        first_free = rhs.first_free;        cap = rhs.cap;        rhs.elements = rhs.first_free = rhs.cap = nullptr;    }    return *this;}String(String &&) noexcept;String& operator=(String&&) noexcept;String::String(String &&s) noexcept : elements(s.elements), end(s.end){    s.elements = s.end = nullptr;}String& String::operator = (String &&rhs) noexcept{    if (this != &rhs) {        free();        elements = rhs.elements;        end = rhs.end;        rhs.elements = rhs.end = nullptr;    }    return *this;}Message(Message &&m); Message& operator=(Message&&); Message::Message(Message &&m) : contents(std::move(m.contents)){    move_Folders(&m);}Message& Message::operator= (Message &&rhs){    if (this != &rhs)    {        remove_from_Folders();        contents = std::move(rhs.contents);        move_Folders(&rhs);    }    std::cout << "Message members moved" << std::endl; // debug    return *this;}

13.50

String baz(){    String ret("world");    return ret; //1}String s5 = baz(); //2

13.51
这里会使用移动构造函数而不是拷贝构造函数。

13.52

hp=hp2; //hp2是左值，使用拷贝赋值hp=std::move(hp2); //使用移动赋值详细解释见p478

13.53
@pezy

#include <string>class HasPtr {public:    friend void swap(HasPtr&, HasPtr&);    HasPtr(const std::string &s = std::string());    HasPtr(const HasPtr &hp);    HasPtr(HasPtr &&p) noexcept;    HasPtr& operator=(HasPtr rhs);    //HasPtr& operator=(const HasPtr &rhs);    //HasPtr& operator=(HasPtr &&rhs) noexcept;    ~HasPtr();private:    std::string *ps;    int i;};#include <iostream>inline void swap(HasPtr &lhs, HasPtr &rhs){    using std::swap;    swap(lhs.ps, rhs.ps);    swap(lhs.i, rhs.i);    std::cout << "call swap" << std::endl;}HasPtr::HasPtr(const std::string &s) : ps(new std::string(s)), i(0){    std::cout << "call constructor" << std::endl;}HasPtr::HasPtr(const HasPtr &hp) : ps(new std::string(*hp.ps)), i(hp.i){    std::cout << "call copy constructor" << std::endl;}HasPtr::HasPtr(HasPtr &&p) noexcept : ps(p.ps), i(p.i){    p.ps = 0;    std::cout << "call move constructor" << std::endl;}HasPtr& HasPtr::operator=(HasPtr rhs){    swap(*this, rhs);    return *this;}HasPtr::~HasPtr(){    std::cout << "call destructor" << std::endl;    delete ps;}int main(){    return 0;}

13.54
略

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