CS 342 - 1/14/16

Programming Paradyms
- Generic/Imperative/Procedural (C, BASIC, FORTRAN...)
- Functional  (LISP, SCHEME, F#)
- Logical (Prolog)
- Object Oriented PL

Commuications of the ACM, 1972
   Parnas Article

    Traditional Languages 
      - Straight foreward Decomposition
      - Modules sharing large data structures through 
           global variables
      - Difficulties is understanding and maintaining software

    Data-Oriented Decomposition
      - soon renamed to "Object-Oriented"
      - High Module independence through small interfaces
      - clear separation of module specifiactions
      - better reuse and ease of maintenance


   Criteria for decomposition
     - Information Hiding 
          - hide implementation and representation details
          - reduced the size of modules

          "Parnas' Law - Only what is hidden can be 
                          changed without risk."

     - Data Abstraction
          combining the storage structure and the operations


Instead of asking "What steps are needed to execute to solve
                        the problem?"

    ask: "What is the best way to organize our data to solve 
                         the problem?"


2D Point data

    Data?
       x, y:   int

    Operations?
       distanceFromOrigin
       setters/getters
       Constructors
       distanceFromOtherPoint


Access modifiers:
  - public         - can be accessed from anywhere
  - protected      - can be access from inside the class and inside
                       of any class that inherits the original class
  -   (default)    - JAVA-special access modifier that allows for
                       access from any point in the package that
                       contains the class
  - private        - can only be accessed from inside the class

Because of the interaction between packages in JAVA and the
   default access modifier, when packages are not used, JAVA
   really only have two access modifiers:

     - private
     - everything else (which appear to act like public)

  // code would be placed in a file called Point2D.java
 public class Point2D
   {
      // Instance Variables or Data Members
      private int x;
      private int y;

      // Methods or Class Operations
      public double distanceFromOrigin (  )
       {
          ...
       }


   }