CODEWITHSUNDEEP
c++listsortingpointers
4pie0
4pie0

Reputation: 29724

list<myClass<int> * > sort

I cannot sort the list which contains the pointers to objects of my template class. template

class Node{
public:
    Node(void){}
    Node(T choice, vector<T> & data);
    Node(T choice, vector<T> & data, player p, int level, int pos, Node<T> *pred, which side);
    void addNodes(void);
    static list<Node<T> * > Nodes;
    friend class MyBinomialTree<Node<T>, T>;
    bool sorter(const Node<T> * lhs, const Node<T> * rhs);// as * &lhs doesn't work too
private:
    Node<T> * left;
    Node<T> * right;
    T chosen_;
    vector<T> data_;
    bool isLeaf;
    //...
};

outside the class:

template<class T>
bool Node<T>::sorter(const Node<T> * lhs, const Node<T> * rhs){
    if((*lhs).level_==(*rhs).level_){
        return (*lhs).pos_<(*rhs).pos_;
    }else{
        return (*lhs).level_<(*rhs).level_;
    }

}

and then I want to sort before print, I have

template<class T>
void Node<T>::print(void){

    std::sort(Node<T>::Nodes.begin(),Node<T>::Nodes.end(),&Node<T>::sorter);
    cout<<endl<<"after sort:"<<endl;

    list<Node<T> * >::iterator it=Node<T>::Nodes.begin();cout<<endl;
    while(it!=Node<T>::Nodes.end()){
    //...
    }
}

errors:

c:\program files\microsoft visual studio 10.0\vc\include\algorithm(3806): error C2784: 'std::complex<_Other> std::operator -(const _Ty &,const std::complex<_Other> &)' : could not deduce template argument for 'const std::complex<_Other> &' from 'std::_List_iterator<_Mylist>'
          with
          [
              _Mylist=std::_List_val<Node<int> *,std::allocator<Node<int> *>>
          ]
          c:\program files\microsoft visual studio 10.0\vc\include\xcomplex(52) : see declaration of 'std::operator -'
          c:\documents and settings\cf16r\moje dokumenty\visual studio 2010\projects\binomial_tree\binomial_tree\mybinomialtree.h(136) : see reference to function template instantiation 'void std::sort<std::_List_iterator<_Mylist>,bool(__thiscall Node<T>::* )(const Node<T> *,const Node<T> *)>(_RanIt,_RanIt,_Pr)' being compiled
          with
          [
              _Mylist=std::_List_val<Node<int> *,std::allocator<Node<int> *>>,
              T=int,
              _RanIt=std::_List_iterator<std::_List_val<Node<int> *,std::allocator<Node<int> *>>>,
              _Pr=bool (__thiscall Node<int>::* )(const Node<int> *,const Node<int> *)
          ]

Upvotes: 1

Views: 888

Answers (1)

Gunslinger47
Gunslinger47

Reputation: 7061

std::sort requires random-access iterators, so it cannot be used with std::list iterators.

http://msdn.microsoft.com/en-us/library/ecdecxh1(v=vs.100).aspx

Make sure you read the documentation for template functions carefully. Template errors can be a nightmare to deal with.

Edit:
As Christian mentioned, std::list has its own sort method. You could just make these two changes:

bool sorter(const Node<T> * lhs, const Node<T> * rhs);
static bool sorter(const Node<T> * lhs, const Node<T> * rhs);

std::sort(Node<T>::Nodes.begin(),Node<T>::Nodes.end(),&Node<T>::sorter);
Nodes.sort(&Node<T>::sorter);

Upvotes: 2

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