ICOM 4015 Advanced Programming

1. ICOM 4015 Advanced Programming Lecture 19 Data Abstraction II Reading: Chapter 6 Prof. Bienvenido Vélez ICOM 4015

2. Data Abstraction IIOutline • Constructors/Destructors • Encapsulation ICOM 4015

3. The List Class // listsClass.h // Global declarations for List ADT typedef int DatumType; class Node; class List { private: Node* first; Node* last; Node* cursor; bool atEnd; bool atStart; long length; // Operations on linked lists public: // List construction and destruction List (); // Constructor without parameters List (DatumType element); // Constructor with parameter List (const List& l); // Copy constructor ~List (); // List modification List& Append (DatumType d); List& Prepend (DatumType d); List& Insert (DatumType d); List& Delete (); // List interation (bidirectional) DatumType First (); DatumType Last (); DatumType Next (); DatumType Prev (); DatumType Current (); bool BOL (); // True if at the beginning of l bool EOL (); // True if at the end of l // List printing void Dump (); }; ICOM 4015

4. Using the List Class #include <iostream> #include "listsClass.h" int main() { // Define the list List l; // Initialize the list. Done by constructor // Fill the list for(int i=0; i<10; i++) { l.Append(i); } // Print the list cout << "List contents:" << endl; for(DatumType d=l.First(); !l.EOL(); d=l.Next()) { cout << "Next datum: " << d << endl; } } Again, no explicit dependencies on pointer implementation of the ADT ICOM 4015

5. Cannot break abstraction barrier! #include <iostream> #include "listsClass.h" int main() { // Define the list List l; // Initialize the list. Done by constructor // Fill the list for(int i=0; i<10; i++) { l.Append(i); } // Print the list cout << "List contents:" << endl; for(DatumType d=l.First(); !l.EOL(); d=l.Next()) { cout << "Next datum: " << d << endl; } cout << "Breaking the abstration barrier" << endl; cout << "List contents:" << endl; for(Node* n=l.first; n!=(Node *) NULL; n=n->next) { cout << "Next datum: " << n->datum << endl; } // Recicle memory occupied by list. Done by destructor } g++ listsClass.cc mainClass.cc -o mainClass mainClass.cc: In function `int main()': mainClass.cc:21: member `first' is a private member of class `List' mainClass.cc:21: invalid use of undefined type `class Node' mainClass.cc:22: invalid use of undefined type `class Node' Compilation exited abnormally with code 1 at Wed Mar 29 08:29:55 ICOM 4015

6. Encapsulation • Package data and functions (members) into a single object structure • Control access to members in order to prevent unwanted dependencies on implementation details ICOM 4015

7. List Class Definition IConstructors/Destructor // List construction and destruction List::List() // Constructor without parameters { List& l = *this; l.first = NullNode; l.last = NullNode; l.cursor = NullNode; l.length = 0; l.atEnd = true; } List::List(DatumType d) // Constructor with parameter { List& l = *this; l.first = NullNode; l.last = NullNode; l.cursor = NullNode; l.length = 0; l.atEnd = true; l.Append(d); } List::List(const List& l) // Copy constructor { cout << "Calling copy construtor" << endl; List& result = *this; result.first = NullNode; result.last = NullNode; result.cursor = NullNode; result.length = 0; result.atEnd = true; for(Node* n = l.first; n!=NullNode; n=n->next) { result.Append(n->datum); } } List::~List() { cout << "Calling destructor" << endl; List& l = *this; Node* n=l.first; while (n!=NullNode) { Node* temp = n; n=n->next; delete temp; } } ICOM 4015

8. List Class Definition IIMethods // List modification List& List::Append(DatumType d) { List& l = *this; Node* temp = new Node; temp->next = NullNode; temp->prev = NullNode; temp->datum = d; if (l.first == NullNode) { l.first = temp; l.last = temp; } else { Node* prev = l.last; prev->next = temp; temp->prev = prev; l.last = temp; } l.length++; return l; } List& List::Prepend(DatumType d) { List& l = *this; Node* temp = new Node; temp->datum = d; temp->next = l.first; temp->prev = NullNode; if (l.first == NullNode) { l.first = temp; l.last = temp; } else { l.first->prev = temp; l.first = temp; } l.length++; } ICOM 4015

9. Using the List Class // mainClass.cc #include <iostream> #include <cmath> #include "listsClass.h" // Forward declarations List sqr(List l); int main() { // Define the list List l; // Initialize the list. Done by constructor // Fill the list for(int i=0; i<10; i++) { l.Append(i); } // Print the list cout << "List contents:" << endl; for(DatumType d=l.First(); !l.EOL(); d=l.Next()) { cout << "Next datum: " << d << endl; } List l2 = sqr(l); cout << "List contents:" << endl; for(DatumType d=l2.First(); !l2.EOL(); d=l2.Next()) { cout << "Next datum: " << d << endl; } } List sqr(List l) { List result; for(DatumType d=l.First(); !l.EOL(); d=l.Next()) { result.Append(d*d); } return result; } ICOM 4015

10. Using the List ClassOutput [bvelez@amadeus] ~/icom4015/lec19 >>mainClass List contents: Next datum: 0 Next datum: 1 Next datum: 2 Next datum: 3 Next datum: 4 Next datum: 5 Next datum: 6 Next datum: 7 Next datum: 8 Next datum: 9 Calling copy construtor Calling copy construtor Calling destructor Calling destructor List contents: Next datum: 0 Next datum: 1 Next datum: 4 Next datum: 9 Next datum: 16 Next datum: 25 Next datum: 36 Next datum: 49 Next datum: 64 Next datum: 81 Calling destructor Calling destructor [bvelez@amadeus] ~/icom4015/lec19 >> ICOM 4015