Re: nest templates class problem

From:
cbarron3@ix.netcom.com (Carl Barron)
Newsgroups:
comp.lang.c++.moderated
Date:
Sun, 22 Apr 2007 23:46:20 CST
Message-ID:
<1hwznd9.11lmoab1s49ubkN%cbarron3@ix.netcom.com>
Eddy Xu <eddyxu@gmail.com> wrote:

Now I have two template classes:
template<
        typename Key,
        typename Value
        typename Op
        >
class Node{
    ....
public:
     int append(Node *node) { return op_.append(node));
....
private:
   Op op_;
}

And I wish to define a Node_XXX_Children to separate the operations
on node children, so that
I can use Node<Key, Value, Node_Map_Childrend>, and etc, to provide
different strategy to deal with child node.

template<
        typename Key,
        >
Node_Map_Children{
public:
      int append(Node *node) { ctn_[node->key] = node; return 0;}
private:
     std::map<Key, Node*> ctn_;
};

But it's nested template define. How can I resolve it?

Thanks for advices.


   Why not mix classic OOP and templates derived from a base class.
then the 'tree' can contain Children containing nodes of Children
constaining nodes or a mixture of Op nodes and Children containing
nodes.

Not tested but something like this.

template <class Key>
struct node_base
{
    Key key;
    virtual ~node_base(){}
    virtual int append(node_base *)=0;
};

template <class Key,class Op>
class op_node:public node_base<Key>
{
         Op op;
public:
    explicit op_node(const Op &a):op(a)
    int append(node_base * p)
    {
         return op(o);
    }
};

template <class Key>
class parent_node:public node_base<Key>
{
    std::map<Key,node_base *> children;
public:
    int append (node_base * p)
    {
        children[p->key] - p;
        return 0;
    }
};

etc.

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