// TEMPLATE FUNCTION _Unchecked
template<class _Iter> inline
    _Iter _Unchecked(_Iter _Src)
    {    // construct unchecked from checked, generic
    return (_Src);
    }

        // TEMPLATE FUNCTION _Rechecked
template<class _Iter,
    class _UIter> inline
    _Iter& _Rechecked(_Iter& _Dest, _UIter _Src)
    {    // reset checked from unchecked, generic
    _Dest = _Src;
    return (_Dest);
    }

它们的作用是什么？没看懂。