class xr_vector : public std::vector<T,allocator> {
private:
    typedef std::vector<T,allocator>    inherited;

public:
    typedef allocator                   allocator_type;

public:
            xr_vector           ()                                  : inherited ()                  {}
            xr_vector           (size_t _count, const T& _value)    : inherited (_count,_value)     {}
    explicit xr_vector          (size_t _count)                     : inherited (_count)            {}
    u32     size                () const                            { return (u32)inherited::size();}

    void    clear_and_free      ()                                  { inherited::clear();           }
    void    clear_not_free      ()                                  { erase(begin(),end());         }
    void    clear_and_reserve   ()                                  { if ( capacity() <= (size()+size()/4) ) clear_not_free(); else { u32 old=size(); clear_and_free(); reserve(old); } }