//node implementation with the composite design pattern

class VarBinNode

{

public:

virtual ~VarBinNode() {}

virtual bool isLeaf() =0;

virtual void traverse() =0;

};

class LeafNode : public VarBinNode

{

private:

Operand var;

public:

LeafNode(const Operand& val) {var=val;}

bool isLeaf() {return true;}

Operand value() {return var;}

void traverse() {cout << "Leaf: " << value() << endl;}

};

class IntlNode : public VarBinNode

{

private:

VarBinNode* lc;

VarBinNode* rc;

Operator opx;

public:

IntlNode(const Operator& op, VarBinNode* l, VarBinNode* r)

{opx=op;lc=l;rc=r;}

bool isLeaf() {return false;}

VarBinNode* left() {return lc;}

VarBinNode* right() {return rc;}

Operator value() {return opx;}

void traverse()

{

cout << "Internal: " << value() << endl;

if (left() != NULL) left()->traverse();

if (right() != NULL) right()->traverse();

}

};

void traverse(VarBinNode* root)

{

if (root != NULL) root->traverse();

}