novice wrote:
Using STL I wanted to create a vector of pointers.For this purpose i have defined a class thin_ptr as follows: //thin_ptr template <typename T ,const bool tAutoDestroy = false> struct thin_ptr { typedef T wrapped_type; T* p;thin_ptr(T* p) {this->p = p;} thin_ptr(const thin_ptr& x) {this->operator=(x);} ~thin_ptr() { if (tAutoDestroy) destroy(); } int destroy() {delete p; p = 0; return 0;} T* release() {T* tp = p; p = 0; return tp;} T* operator -> () const { return p;} T& operator * () const { return *p;} T** operator & () const {return &p;} operator T* () const { return p;} T* operator = (T* p) {this->p = p;} // for STL containers bool operator < (const thin_ptr& x) const { return *p < *x.p;} bool operator!() const {return p == 0;} }; which is giving the error: In member function `T** thin_ptr<T, tAutoDestroy>::operator&() const [with T = TSPGene<RandomCRT>, bool tAutoDestroy = false]': /usr/include/c++/3.2.2/bits/stl_uninitialized.h:87: instantiated from `_ForwardIter std::__uninitialized_copy_aux(_InputIter, _InputIter, _ForwardIter, __false_type) [with _InputIter = __gnu_cxx::__normal_iterator<thin_ptr<TSPGene<RandomCRT>, false>*, std::vector<thin_ptr<TSPGene<RandomCRT>, false>, std::allocator<thin_ptr<TSPGene<RandomCRT>, false> > > >, _ForwardIter = __gnu_cxx::__normal_iterator<thin_ptr<TSPGene<RandomCRT>, false>*, std::vector<thin_ptr<TSPGene<RandomCRT>, false>, std::allocator<thin_ptr<TSPGene<RandomCRT>, false> > > >]' /usr/include/c++/3.2.2/bits/stl_uninitialized.h:112: instantiated from `_ForwardIter std::uninitialized_copy(_InputIter, _InputIter, _ForwardIter) [with _InputIter = __gnu_cxx::__normal_iterator<thin_ptr<TSPGene<RandomCRT>, false>*, std::vector<thin_ptr<TSPGene<RandomCRT>, false>, std::allocator<thin_ptr<TSPGene<RandomCRT>, false> > > >, _ForwardIter = __gnu_cxx::__normal_iterator<thin_ptr<TSPGene<RandomCRT>, false>*, std::vector<thin_ptr<TSPGene<RandomCRT>, false>, std::allocator<thin_ptr<TSPGene<RandomCRT>, false> > > >]' /usr/include/c++/3.2.2/bits/stl_vector.h:903: instantiated from `void std::vector<_Tp, _Alloc>::_M_insert_aux(__gnu_cxx::__normal_iterator<_Tp*, std::vector<_Tp, _Alloc> >, const _Tp&) [with _Tp = thin_ptr<TSPGene<RandomCRT>, false>, _Alloc = std::allocator<thin_ptr<TSPGene<RandomCRT>, false> >]' /usr/include/c++/3.2.2/bits/stl_vector.h:498: instantiated from `void std::vector<_Tp, _Alloc>::push_back(const _Tp&) [with _Tp = thin_ptr<TSPGene<RandomCRT>, false>, _Alloc = std::allocator<thin_ptr<TSPGene<RandomCRT>, false> >]' Main6.h:1194: instantiated from here Main6.h:679: invalid conversion from `TSPGene<RandomCRT>* const*' to ` TSPGene<RandomCRT>**' ////////////////////////////////////////////////////////////////////////////////////////
I think the problem is that operator&() is a const method, which makes the member variable thin_ptr<T>::p implicitly a const pointer (i.e. T*const), so that &p is T*const *. You need a const_cast to make the conversion from T* const * to T**. Alternatively, remove the const from operator&().
The latter choice is your better bet. _______________________________________________ help-gplusplus mailing list help-gplusplus@gnu.org http://lists.gnu.org/mailman/listinfo/help-gplusplus
