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 = { 1,2,3,4,5 };
      //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,10,_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 = { 1,2,3,4,5 };
      //绑定仿函数
      for_each(myint.begin(), myint.end(), bind(addit(), 10, _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(10);
      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(2));
      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 = 0; i < 10; 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("123") + fun("34") << endl;
  
      fun = strlen;
      cout << fun("234") << 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 = 4;
      //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>("849");
      cout << i << endl;//转换失败则显示异常
  
      char str[5] = { '1','2','3','4','5' };
      i = boost::lexical_cast<int>(str, 5);
      cout << i << endl;
  
      cin.get();
  }
  
  //转换成字符串类型
  void main8()
  {
      std::string str = boost::lexical_cast<std::string>("12345");
      cin.get();
  }
  
  void main9()
  {
      std::string str = boost::lexical_cast<std::string>("12345");
      //转换安全(转换失败会报异常)
      int num = boost::numeric_cast<int>("1234");
      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();
  }