9.variant move function change_cast

• 包含的头文件

   #include <iostream>
   #include <string>
   #include <boost/array.hpp>
   //异构的容器
   #include <boost/any.hpp>
   #include <vector>
   #include <typeinfo>
   #include <algorithm>
   #include <boost/bind.hpp>
   #include <functional>
   #include <boost/variant.hpp>
   #include <boost/move/move.hpp>
   #include <boost/function.hpp>
   #include <boost/bind.hpp>
   #include <boost/lexical_cast.hpp>
   #include <boost/numeric/conversion/cast.hpp>
   #include <boost/cast.hpp>
   using namespace std;
   using namespace boost;

• 函数包装器,包装仿函数,以及一个类包装另外一个类的函数

   int add(int a, int b)
   {
       cout << a + b << endl;
       return a + b;
   }
  
   //常规包装器
   void main1()
   {
       vector<int> myint = { ,,,, };
       //绑定操作
       //for_each(myint.begin(), myint.end(), bind(add, 10, _1));
  
       //绑定lambda表达式,借助函数包装器
       boost::function<void(int,int)> fun = [](int a, int b)
       {
           cout << a + b << endl;
       };
       for_each(myint.begin(), myint.end(), bind(fun,,_1));
       cin.get();
   }
  
   //继承异构二元操作类
   class addit :public std::binary_function<int, int, void>
   {
   public:
       void operator()(int i, int j)
       {
           cout << i + j << endl;
       }
   };
  
   //绑定仿函数
   void main2()
   {
       vector<int> myint = { ,,,, };
       //绑定仿函数
       for_each(myint.begin(), myint.end(), bind(addit(), , _1));
       cin.get();
   }
  
   void main3()
   {
       //myv可以是四种类型之一的任何一种类型
       typedef boost::variant<int, double, char, const char *> myv;
       std::vector<myv> s_values;
       s_values.push_back();
       s_values.push_back('X');
       s_values.push_back(10.9);
       s_values.push_back("hello");
       s_values.push_back('z');
       //根据数据类型来获取
       char ch = boost::get<char>(s_values.back());
       double db = boost::get<double>(s_values.at());
       cout << db << endl;
  
       cin.get();
   }
  
   //manager管理worker 类与类之间通信
   class manager
   {
   public:
       //函数指针
       boost::function<void(int)> workid;
       void setcallback(boost::function<void(int)> newworkid)
       {
           workid = newworkid;
       }
  
       void allgo()
       {
           for (int i = ; i < ; i++)
           {
               if (workid)
               {
                   workid(i);
               }
           }
       }
   };
  
   class worker
   {
   public:
       int id;
       void run(int toid)
       {
           id = toid;
           cout << id << "干活" << endl;
       }
   };
  
   void main6()
   {
       manager m;
       worker w;
       //传递一个绑定的函数,调用者是w,需要一个参数
       m.setcallback(boost::bind(&worker::run, &w, _1));
       m.allgo();
       cin.get();
   }

   //function
   void main5()
   {
       boost::function<int(char *)>fun = atoi;
       cout << fun("") + fun("") << endl;
  
       fun = strlen;
       cout << fun("") << endl;
       cin.get();
   }

• 左值转化为右值

   //右值引用
   void show(int &&data)
   {
       cout << data << endl;
   }
  
   void main4()
   {
       int a = ;
       //左值转化为右值
       show(std::move(a));
       show(boost::move(a));
       cin.get();
   }

• 类型转换与类类型之间的转换,失败会异常

   //类型转换
   void main7()
   {
       int i = boost::lexical_cast<int>("");
       cout << i << endl;//转换失败则显示异常
  
       char str[] = { '','','','','' };
       i = boost::lexical_cast<int>(str, );
       cout << i << endl;
  
       cin.get();
   }
  
   //转换成字符串类型
   void main8()
   {
       std::string str = boost::lexical_cast<std::string>("");
       cin.get();
   }
  
   void main9()
   {
       std::string str = boost::lexical_cast<std::string>("");
       //转换安全(转换失败会报异常)
       int num = boost::numeric_cast<int>("");
       cin.get();
   }
  
   class A
   {
  
   };
  
   class B :public A
   {
  
   };
  
   //类类型之间的转换
   void main()
   {
       B bobj;
       //转换失败会报异常
       boost::polymorphic_cast<A*>(&bobj);
       cin.get();
   }