Boost::any Learning

#include <iostream> #include <typeinfo> #include <list>using namespace Std;class any{public:// Interface class Placeholder {public://Virtual ~placeholder () {}//Virtual const ST        d::type_info& type () const = 0;    Virtual placeholder * Clone () const = 0;    }; Template<typename valuetype> class Holder:public placeholder {public://structors Holder ( Const ValueType & Value): Held (value) {}//Virtual const std::type_info& type () CO        NST {return typeid (ValueType);        }//Virtual Placeholder * Clone () const {return new holder (held);    } public://representation ValueType held; };p Ublic:any (): content (0) {} template<typename valuetype> any (const ValueType & value): Conten T (new holder<valuetype> (value)) {}//copy constructor any (const all & Other): Content (other.content? Other.content->clone (): 0) {}//Move constructor    Any (any&& other): Content (other.content) {other.content = 0; }//Perfect forwarding of ValueType template<typename valuetype> any (valuetype&& value): Content (n    EW holder< typename Decay<valuetype>::type > (static_cast<valuetype&&> (Value))) {}//    ~any () {delete content;        }//any & swaps (any & RHS) {std::swap (content, rhs.content);    return *this;        }//any & operator= (const any& RHS) {any (RHS). Swap (*this);    return *this;        }//Move assignement any & operator= (any&& rhs) {rhs.swap (*this);        Any (). Swap (RHS);    return *this; }//Perfect forwarding of ValueType template <class valuetype> any & operator= (valuetype&& RHS ) {Any (STATic_cast<valuetype&&> (RHS)). Swap (*this);    return *this;    }//bool empty () const {return!content;    }//void Clear () {any (). Swap (*this);    } //。    Const std::type_info& Type () const {return content? Content->type (): typeid (void);    }private://representation template<typename valuetype> friend ValueType * Any_cast (any *);    Template<typename valuetype> friend ValueType * Unsafe_any_cast (any *); placeholder * content;}; inline void swap (any & LHS, any & RHS) {Lhs.swap (RHS);} Class Bad_any_cast:public std::bad_cast{public://Virtual const char * what () const//{//return "boost::b Ad_any_cast: "//" failed conversion using boost::any_cast ";//}};template<typename Valuetype>value Type * ANY_CAST (any * operand) {return operand && operand->type () = = typeID (ValueType)? &static_cast< Any::holder<valuetype>*>(operand->content)->held:0;} Template<typename valuetype>inline Const VALUETYPE * ANY_CAST (const any * operand) {return any_cast<valuetype& gt; (Const_cast<any *> (operand));} Template<typename valuetype>inline ValueType any_cast (const any & operand) {Const VALUETYPE * result = Any_ca    St<valuetype> (&operand);    if (!result) throw bad_any_cast (); return *result;}    int main () {typedef std::list<any> list_any;    List_any list;    List.push_back (10);    List.push_back (std::string ("std::string type"));    Const CHAR* p = "Const char* string";    List.push_back (P); for (const auto& elem:list) {if (elem.type () = = typeid (int)) Std::cout<<any_cast<int&gt        ;(elem) <<std::endl; else if (elem.type () = = typeID (std::string)) std::cout<<any_cast<std::string> (elem) <<std::en        dl else if (elem.type () = = typeid (const char*)) std::cout<<any_cast<Const char*> (elem) <<std::endl; } return 0;}

Boost::any Learning