shared_ptr<> reset

// std_tr1__memory__shared_ptr_reset.cpp
// compile with: /EHsc
#include <memory>
#include <iostream> 

struct deleter
{
    void operator()(int *p)
    {
        delete p;
    }
}; 

int main()
{
    std::shared_ptr<int> sp(new int());
    //std::boolalpha bool类型输出为true或者false而不是0或者1,默认输出0和1
    //reset更换管理对象
    std::cout << "*sp == " << std::boolalpha
        << *sp << std::endl; 

    sp.reset();
    std::cout << "(bool)sp == " << std::boolalpha
        << (bool)sp << std::endl; 

    sp.reset(new int());
    std::cout << "*sp == " << std::boolalpha
        << *sp << std::endl; 

    sp.reset(new int(), deleter());
    std::cout << "*sp == " << std::boolalpha
        << *sp << std::endl;
    getchar();
    return ();
} 

reset用处很多，其中的原理啥的还需探究