C++ 学习（右值引用， std::move)

1.std::move执行一个无条件的转化到右值。它本身并不移动任何东西；

2.std::forward把其参数转换为右值，仅仅在那个参数被绑定到一个右值时；

3.std::move和std::forward在运行时（runtime）都不做任何事。
#include <iostream>
#include <stdio.h>
#include <algorithm>
#include <stdlib.h>
#include <ext/memory>
#include <vector>
#include <set>
#include <string.h>

using namespace std;

class Quote{
public:
string ISBN;
double price;
Quote() = default;
Quote(const string &book, const double p):ISBN(book), price(p){};
virtual   Quote* clone() const & {
return new Quote(*this);
}
virtual Quote* clone()&& {
return new Quote(std::move(*this));
}
public:
string isbn() const;
virtual double net_price(size_t n) const{
return n * price;
}
};

class Bulk_quote: public Quote{
private:
size_t min_qty = 0;
double discount = 0.9;
Bulk_quote() = default;
Bulk_quote(const string &book, double p, size_t qty, double disc):
Quote(book, p), min_qty(qty), discount(disc){};
public :
double net_price(size_t cnt) const {
if(cnt >= min_qty)
return cnt*(1-discount)*price;
else
return cnt * price;
}

Bulk_quote *clone() const &{return new Bulk_quote(*this);};
Bulk_quote *clone() const &&{return new Bulk_quote(std::move(*this));};
};

double print_total(ostream &os, const Quote &item, size_t n){
double ret = item.net_price(n);
os<<"ISBN :"<<item.isbn() << " # sold: "<<n<<" total due:  "<<ret<<endl;
return ret;
}

class Basket{
public :
void add_item(const shared_ptr<Quote> &sale){
items.insert(sale);
}
void add_item(const Quote &sale){
items.insert(shared_ptr<Quote> (sale.clone()));
}
void add_item(const Quote && sale){
items.insert(shared_ptr<Quote>(std::move(sale).clone()));
}
double total_receipt(ostream & os) const{
double sum = 0.0;
for(auto iter = items.cbegin(); iter != items.cend(); iter = items.upper_bound(*iter)){
sum += print_total(os, **iter, items.count(*iter));
}
os<<"Total Sale: "<<sum <<endl;
return sum;
}
private:
static bool compare(const shared_ptr<Quote> &lhs, const shared_ptr<Quote> &rhs){
return lhs->isbn() < rhs->isbn();
}
std::multiset<shared_ptr<Quote>, decltype(compare)*>items;
};

int main()
{

}