vc2010中的c++11特性探索-白红宇

vc2010中的c++11特性探索

阅读量：6877 次

发布时间：2019-06-26

本文共 1763 字，大约阅读时间需要 5 分钟。

#include 
     
      #include 
      
       using namespace std;struct W{    W(int&, int&) {}};struct X{    X(const int&, int&) {}};struct Y{    Y(int&, const int&) {}};struct Z{    Z(const int&, const int&) {}};template 
       
        T* factory(A1&& a1, A2&& a2){    return new T(std::forward
        
         (a1), std::forward
         
          (a2));}int&& haha(int&& a){    cout<< "before haha, a is " << a <

(a);}int _tmain(int argc, _TCHAR* argv[]){ char s[]="Hello World!"; int Uppercase = 0; for_each(s,s+sizeof(s),[&](char c) { if(isupper(c)) Uppercase++; }); cout<

<< " uppercase letters in: " << s << endl; /* int my_array[]={1,2,3,4,5,6}; for (int& x : my_array) { cout << x <

(a, b); X* px = factory

(2, b); Y* py = factory

(a, 2); Z* pz = factory

(2, 2); delete pw; delete px; delete py; delete pz; cout << "first a is :" << a <

(a)); cout<< "really a is :" << a <

明天再看看。

早上来仔细研究了下右值的作用，先定义一个类来捕获各种拷贝

class A{public:    A(const string& s = ""):itsFather(s){ cout << itsFather << ": A Constructor\n";}    A(A&& A){ cout << itsFather << ": move constructor" <
     
      << endl;return *this;}    ~A() { cout << itsFather << ": A Destructor\n";}    string itsFather;    A(const A& a){ cout << itsFather << ": copy constructor" <

再定义2个函数对比下效果：

A getA(){    A temp("GetA");    return temp;// forward(temp);}A GetMoveA(){    A temp("GetMoveA");    return std::move(std::forward(temp));}

cout<<"\n\n\n\n";    A B = getA();    cout<<"\n\n\n\n";    A C = GetMoveA();

看看输出结果，好奇怪：

GetA: A Constructor: move constructorGetA: A DestructorGetMoveA: A Constructor: move constructorGetMoveA: A Destructor: A Destructor: A Destructor

原本的方法反而更有效了。第二种方法多了2个临时对象的析构，但这2个都没有copy。

转载于:https://www.cnblogs.com/zhangyonghugo/archive/2012/07/06/2578664.html