1. General Computer Science for Engineers CISC 106 James Atlas Computer and Information Sciences 11/13/2009

2. Lecture Overview Review ◦ Structures in MATLAB Advanced MATLAB ◦ Classes  isa function  hierarchy ◦ Cell Arrays

3. Structures in MATLAB

4. A Database Application Given= Name= Chris Credits= 27 Graduation= 12/15/2011 Name= Sola Credits= 18 Graduation= 05/17/2011 Name= Roger Credits= 55 Graduation= 06/10/2009 Name= Tom Credits= 15 Graduation= 05/22/2012

5. Given= We can implement it with arrays like this= Name Credits Grad. 1 2 3 4 Name= Chris Credits= 27 Graduation= 12/15/2011 Name= Sola Credits= 18 Graduation= 05/17/2011 Name= Roger Credits= 55 Graduation= 06/10/2009 Name= Tom Credits= 15 Graduation= 05/22/2012 27Chris12/15/2011 18Sola05/17/2011 55Roger06/10/2009 15Tom05/22/2012 A Database Application

6. Given= OR we can do it like this an array with structs=.d Name= Chris Credits= 27 Graduation= 12/15/2011 Name= Sola Credits= 18 Graduation= 05/17/2011 Name= Roger Credits= 55 Graduation= 06/10/2009 Name= Tom Credits= 15 Graduation= 05/22/2012 Students (1). Name= ‘Chris’ Students (1).Credits= 27 Students (1). Graduation= ‘12/15/2011’ Students (2).Name= ‘Sola’ Students (2).Credits= 18 Students (2).Graduation= ‘05/17/2011’ Students (3). Name= ‘Roger’ Students (3). Credits= 55 Students (3). Graduation= ‘06/10/2009’ Students (4). Name= ‘Tom’ Students (4). Credits= 15 Students (4). Graduation= ‘05/22/2012’ A Database Application

7. record1.name = 'Me'; record2.name = 'Not Me'; record1.credits = 27; record2.credits = 30; record1.age = 10; record2.age = 14; function [] = displayRecordName(record) disp(record.name); displayRecordName(record1); displayRecordName(record2); Initializing a structure

8. Classes Object-oriented Programming Classes represent types of Objects Similar to structs

9. Class definition classdef Student properties name credits age end

10. Class definition (cont’) classdef Student properties name credits age end methods function obj=Student(name, credits, age) obj.name = name; obj.credits = credits; obj.age = age; end

11. Class definition classdef Teacher properties name yearsTaught age end methods function obj= Teacher(name, yearsTaught, age) obj.name = name; obj.yearsTaught = yearsTaught; obj.age = age; end

12. Common properties? Student name credits age Teacher name yearsTaught age

13. Common properties (cont’)? Student credits Teacher yearsTaught Person name age An example of the “is a” relationship. A Student “is a” Person. A Teacher “is a” Person. The Person class contains shared properties.

14. Class definition (Person) classdef Person properties name age end methods function obj = Person(name, age) obj.name = name; obj.age = age; end

15. Class definition (Student) classdef Student < Person properties credits end methods function obj = Student(name, age, credits) obj@Person(name,age); obj.credits = credits; end

16. Class definition (Teacher) classdef Teacher < Person properties yearsTaught end methods function obj = Teacher(name, age, yearsTaught) obj@Person(name,age); obj.yearsTaught = yearsTaught; end

17. The isa function isa(object, ‘classname’) Examples= student1 = Student(‘Frank’,25,20); teacher1 = Teacher(‘James’,0,30); isa(student1, ‘Student’) isa(teacher1, ‘Teacher’) isa(student1, ‘Teacher’) isa(student1, ‘Person’)

18. Arrays of classes? student1 = Student(‘Frank’,25,20); student2 = Student(‘Sally’,50,21); teacher1 = Teacher(‘James’,0,30); [student1 student2] [student1 student2 teacher1] ?

19. Cell Arrays Normal array zeros(1,5) is 5 doubles [1 2 3 4] is 4 doubles Cell array {1 2 3 4} is 4 cells, each with a 1x1 array of double values inside

20. What is a cell? A cell is like a window into a room, and inside the room can be data of any size A cell array is like a hallway with many doors 15437 52 Student age=19 name=‘Joe’ credits=78 ‘hello’ 0 1.1 normal arraycell array

21. Cell Arrays (cont) c = {1 2 3 4} c{1} = ‘hello’ Cell arrays store cells ◦ Can be another array ◦ Or a string ◦... any struct/object/cell array