/*
--- CSU213 Spring 2005 Lecture Notes ---------
Copyright 2005 Viera K. Proulx

Lecture 1: All I Ever Needed to Know I Learned in Kindergarden
*/

/* 
Goals:

 - recall data definitions from HtDP
 - translate data definitions into class diagrams and Java code
 - understand that the concepts are the same

Consider the library catalog that contains information about books, CDs,
and magazines. What information does it contain?

Books: title, author, catalog number, ... and more
CDs: title, artist, number of tracks, catalog number, ... and more
Magazines: title, volume or year, issue, catalog number, ... and more

Let us make examples of this kind of data:
  book: Cat in a Hat by Dr Seuss, number 77
  book: HtDP, by Matthias, number 42

  cd: Thriller, with Michael Jackson, 10 tracks, number 99
  cd: Pearl, by Janis Joplin, 12 tracks, number 88

  magazine: Time, issue 52 in 2004, number 33
  magazine: Wired, issue 3 in 2004, number 44


The data definition in HtDP would then be:

;;A Library item is one of 
  (define-struct book (title author no))
   ;; where title and author are Strings and no is a Number

  (define-struct cd (title artist tracks no))
   ;; where title and artist are Strings and tracks and no are Numbers

  (define-struct mag (title year issue no))
   ;; where title is a String and year, issue and no are Numbers

and we could make examples of the information shown above represented
as data:

  (define ch (make-book "Cat in a Hat" "Dr Seuss" 77))
  (define htdp (make-book "HtDP" "Matthias F" 42))

  (define thriller (make-cd "Thriller" "Michael Jackson" 10 99))
  (define pearl (make-cd "Pearl" "Janis Joplin" 12 88))

  (define time (make-mag "Time" 2004 52 33))
  (define wired (make-mag "Wired" 2004 3 44))

;; DrScheme then gives us the following functions to deal with this data:

  (book? ch) 
   ;; --> produces true
  (book? pearl)
   ;; --> produces false

  (book-title htdp)
   ;; --> produces "HtDP"
  (book-author ch) 
   ;; --> produces "Dr Seuss"
  (book-no ch) 
   ;; --> produces 77

We have similar functions for the other two structures: cd and mag.

We can represent all the information about books in the following diagram:

+---------------+
| Book          |
+---------------+
| String title  |
| String author |
| int no        |
+---------------+

In Java, this represents a class of data, the component data parts are called 
fields, or member data, and the description of the type of data for each field
has to be explicitly stated as a part of the Java class definition. Each field
can hold only one type of data - we cannot say that author is 
either a String or boolean. We also have to write the constructor explicitly
ourselves, though the code always looks the same. The numbers come in two flavors:
whole numbers, known as 'int' and inexact numbers that typically represent 
fractions, known as 'double'. Later, we will se variations of these.

The complete Java definition of the class Book is shown below:
*/


// to represent a book
class Book {
  String title;
  String author;
  int no;

  Book(String title, String author, int no) {
    this.title = title;
    this.author = author;
    this.no = no;
  }
}

/*
The examples of books then are defined as follows:

  Book ch = new Book("Cat in a Hat", "Dr Seuss", 77);
  Book htdp = new Book("HtDP", "Matthias F", 42);


These definitions can be written in the Interactions Window, or become data
definitions is a class that holds our examples and tests. (See the lab for details.)

For practice, make class diagrams and define Java classes to represent Cds and 
magazines.
*/

/* 
Part 2: Containment

Imagine that we would like more information about the author, such as the year of birth.
It is clear, that the information about the author should not be defined together 
with the book object, as there may be several books written by the same author.

We can design the class to represent authors, and have the class Book contain an 
instance of the class Author. All books written by the same author should contain
the same instance of Author.

Here are the revised examples:

book: HtDP by Matthias, (born in ??1920 - he is not that old, but what do we know),
      catalog number 42

book: ALJaFP by Matthias, (same one), catalog number 29

book Cat in a Hat, by Dr Seuss, born in 1915, catalog number 77

The two class definition then become:
*/

/*
+-------------+
| Author      |
+-------------+
| String name |
| int year    |
+-------------+

*/

// to represent an author
class Author {
  String name;
  int year;

  Author(String name, int year) {
    this.name = name;
    this.year = year;
  }
}
/*
+---------------+
| Book          |
+---------------+
| String title  |
| Author author |
| int no        |
+---------------+

*/

// to represent a book
class Book {
  String title;
  Author author;
  int no;

  Book(String title, Author author, int no) {
    this.title = title;
    this.author = author;
    this.no = no;
  }
}

/*
Additionally, we would like the class diagram to represent the containment
relationship between the two classes. we use 'containment arrow' as follows:


+---------------+
| Book          |
+---------------+
| String title  |
| Author author |---------+
| int no        |         |
+---------------+         v
                   +-------------+
                   | Author      |
                   +-------------+
                   | String name |
                   | int year    |
                   +-------------+


We now need to make exampels of our information represented as instances 
of these classes:

  Author matthias = new Author("Matthias", 1920);
  Author drseuss = new Author("Dr Seuss", 1915);

  Book htdp = new Book("HtDP", matthias, 42);
  Book aljafp = new Book("ALJaFP", matthias, 29);
  Book ch = new Book("Cat in a Hat", drseuss, 77);

*/