- Implement a tree which constructs an expression tree from the prefix form of an arithmetic expression. Example of the prefix form: * + 1 3 6 4 Example of the infix form: (1 + 3) * (6 - 4) Functions to implement: - build() - builds corresponding expression tree: (25 pts) - expression() - converts and outputs prefix form into infix form: (25 pts) - evaluate() - returns the value of corresponding expression tree: (25 pts) - Other functions (constructor, copy constructor, desctructor, clear()) (25 pts) ExpressionTree.h #ifndef EXPRESSIONTREE_H #define EXPRESSIONTREE_H #include #include using namespace std; template class ExprTree { public: // Constructor ExprTree (); ExprTree(const ExprTree& source); ExprTree& operator=(const ExprTree& source); // Destructor ~ExprTree (); // Expression tree manipulation operations void build (); void expression () const; DataType evaluate() const throw (logic_error); void clear (); // Clear tree void commute(); bool isEquivalent(const ExprTree& source) const; bool isEmpty() const; // Output the tree structure -- used in testing/debugging void showStructure () const; private: class ExprTreeNode { public: // Constructor ExprTreeNode ( char elem, ExprTreeNode *leftPtr, ExprTreeNode *rightPtr ); // Data members char dataItem; // Expression tree data item ExprTreeNode *left, // Pointer to the left child *right; // Pointer to the right child }; // Recursive helper functions for the public member functions -- insert // prototypes of these functions here. void buildHelper(ExprTreeNode*& p); void exprHelper(ExprTreeNode* p) const; DataType evalHelper(ExprTreeNode* p) const; void clearHelper ( ExprTreeNode *p ); void showHelper ( ExprTreeNode *p, int level ) const; void copyHelper ( ExprTreeNode *&p ); void commuteHelper(ExprTreeNode* p); bool isEquivalentHelper(const ExprTreeNode* p, const ExprTreeNode* q) const; // Data member ExprTreeNode *root; // Pointer to the root node }; #endif // #ifndef EXPRESSIONTREE_H ExpressionTree.cpp #include "ExpressionTree.h" template ExprTree::ExprTreeNode::ExprTreeNode ( char elem, ExprTreeNode *leftPtr, ExprTreeNode *rightPtr ) { } template ExprTree::ExprTree () { } template ExprTree::ExprTree(const ExprTree& source) { } template ExprTree& ExprTree::operator=(const ExprTree& source) { } template void ExprTree::copyHelper(ExprTreeNode *&p) {} template ExprTree::~ExprTree () { } template void ExprTree::build () { } template <> void ExprTree::buildHelper(ExprTreeNode*& p) {} template <> void ExprTree::buildHelper(ExprTreeNode*& p) {} template void ExprTree::expression () const { } template void ExprTree::exprHelper(ExprTreeNode* p) const {} template DataType ExprTree::evaluate() const throw (logic_error) { DataType temp; return temp; } template <> float ExprTree::evalHelper(ExprTreeNode* p) const { float temp; return temp; } template <> bool ExprTree::evalHelper(ExprTreeNode* p) const { bool temp; return temp; } template void ExprTree::clear () { } template void ExprTree::clearHelper(ExprTreeNode *p) {} template void ExprTree::commute() { } template void ExprTree::commuteHelper(ExprTreeNode* p) {} template bool ExprTree::isEquivalent(const ExprTree& source) const { } template bool ExprTree::isEquivalentHelper(const ExprTreeNode* x, const ExprTreeNode* y) const {} template bool ExprTree::isEmpty() const { return false; } template void ExprTree::showStructure() const // Outputs an expression tree. The tree is output rotated counter- // clockwise 90 degrees from its conventional orientation using a // "reverse" inorder traversal. This operation is intended for testing // and debugging purposes only. { // No isEmpty function in this class. Add a private one if you wish. if (root == 0) cout << "Empty tree" << endl; else { cout << endl; showHelper(root, 1); cout << endl; } } // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - template void ExprTree::showHelper(ExprTreeNode *p, int level) const // Recursive helper for the showStructure() function. Outputs the // subtree whose root node is pointed to by p. Parameter level is the // level of this node within the expression tree. { int j; // Loop counter if (p != 0) { showHelper(p->right, level + 1); // Output right subtree for (j = 0; j < level; j++) // Tab over to level cout << "\t"; cout << " " << p->dataItem; // Output dataItem if ((p->left != 0) && // Output "connector" (p->right != 0)) cout << "<"; else if (p->right != 0) cout << "/"; else if (p->left != 0) cout << "\\"; cout << endl; showHelper(p->left, level + 1); // Output left subtree } } test8.cpp #include #include using namespace std; //#include "ExprTree.cpp" #include "ExpressionTree.cpp" #include "config.h" //-------------------------------------------------------------------- // Function prototype template void dummy ( ExprTree copyTree ); // copyTree is passed by value //-------------------------------------------------------------------- int main() { #if !LAB8_TEST1 || LAB8_TEST2 || LAB8_TEST3 // Don't do this if testing boolean tree, unless also testing programming // exercises 2 or 3 (for which this section is mostly needed). // The tricky part occurs if testing exercise 1 and (2 or 3), or if // someone is trying to test the basic class and one of the other exercises // in parallel. Hence the #if expression above. cout << "Start of testing the basic expression tree" << endl; ExprTree testExpression; // Test expression cout << endl << "Enter an expression in prefix form : "; testExpression.build(); testExpression.showStructure(); testExpression.expression(); cout << " = " << testExpression.evaluate() << endl; // Test the copy constructor. dummy(testExpression); cout << endl << "Original tree:" << endl; testExpression.showStructure(); #endif #if LAB8_TEST1 cout << "Start of testing the boolean expression tree" << endl; ExprTree boolTree; cout << endl << "Enter a boolean expression in prefix form : "; boolTree.build(); boolTree.showStructure(); boolTree.expression(); cout << " = " << boolTree.evaluate() << endl; cout << "** End of testing the boolean expression tree" << endl; #endif #if LAB8_TEST2 cout << "Start of testing commute()" << endl; testExpression.commute(); cout << endl << "Fully commuted tree: " << endl; testExpression.showStructure(); testExpression.expression(); cout << " = " << testExpression.evaluate() << endl; cout << "End of testing commute()" << endl; #endif #if LAB8_TEST3 cout << "Start of testing isEquivalent()" << endl; ExprTree same = testExpression; cout << "same is equal (tests copy constructor) ? "; cout << (same.isEquivalent(testExpression) ? "Yes" : "No") << endl; ExprTree empty; cout << "empty is equal? "; cout << (empty.isEquivalent(testExpression) ? "Yes" : "No") << endl; ExprTree userExpression; cout << "Enter another expression in prefix form: "; userExpression.build(); cout << "new expression is equal? "; cout << (userExpression.isEquivalent(testExpression) ? "Yes" : "No") << endl; cout << "** End of testing isEquivalent()" << endl; #endif #if !LAB8_TEST1 && !LAB8_TEST2 && !LAB8_TEST3 // Don't bother with this if testing any of the programming exercises cout << endl << "Clear the tree" << endl; testExpression.clear(); testExpression.showStructure(); cout << "** End of testing the basic expression tree" << endl; #endif system("PAUSE"); return 0; } //-------------------------------------------------------------------- template void dummy ( ExprTree copyTree ) // Dummy routine that is passed an expression tree using call by // value. Outputs copyTree and clears it. { cout << endl << "Copy of tree: " << endl; copyTree.showStructure(); copyTree.clear(); cout << "Copy cleared: " << endl; copyTree.showStructure(); }