Programming paradigms

A way of thinking about programming

The programmer's mental model

The structure of the approach

The limitations of the solution

A sequence of actions

width_1 = 12.0 height_1 = 27.2 area_1 = width_1 * height_1 width_2 = 93.2 area_2 = width_2 * height_1 height_2 = 47 area_3 = width_1 * height_2 ...

A set of functions, defined and used

    def area(width, height): 
        return width * height 
 
    width_1 = 12.0 
    height_1 = 27.2 
    width_2 = 93.2 
    height_2 = 47 
 
    area_1 = area(width_1, height_1) 
    area_2 = area(width_2, height_1) 
    area_3 = area(width_1, height_2)

But functions are characterized by their inputs

    def area(width, height): 
        return width * height 
 
    width_1 = ? 
    height_1 = ? 
    width_2 = ? 
    height_2 = ?

Functions and data are interdependent

Numeric data, numeric functions

Alphabetic data, alphabetic functions

Image data, image functions

Geometric data, geometric functions

and so forth ...

A new paradigm

Since the functions and data are interdependent, combine them.

This combination is called an object.

Programming with objects is called object-oriented programming.

Object-oriented programming: categories

Abstract description of a thing

A "car"

Concrete example of a thing

My 1988 Honda civic with a banged-up side

Object-oriented programming: qualities

Abstract properties of a thing

     Make
     Model
     License plate number
     Color

Concrete properties of a thing

     Honda
     Civic
     CA 2JPM905
     Brownish

Hey, wait, my car died!

Abstract properties of a thing

     Make
     Model
     License plate number
     Color

Concrete properties of a thing

     Toyota
     Scion xA
     An empty value
     Weird sparkly gray

Newly discovered properties

Target demographic

Object-oriented programming: processes

Abstract actions done by or to a thing

     Start
     Brake
     Steer
     Refuel

Concrete actions done by or to a "car"

     Turn key in ignition
     Push brake pedal
     Turn steering wheel right or left
     Open gas tank, insert nozzle, turn on pump

Object-oriented programming: processes

Abstract actions done by or to a thing

     Start
     Brake
     Steer
     Refuel

Concrete actions done by or to a "sailboat"

     Untie ropes from dock, push off
     Loosen the mainsail, drop anchor
     Turn rudder right or left
     Hope for wind...

Object-oriented inheritance

Shared qualities can be defined as an object

A class to represent "vehicle-ness"

     Position
     Heading
     Speed

A "car" is a "vehicle" specific to land

Generic vehicle-ness + specific car-ness

A "sailboat" is a "vehicle" specific to water

Generic vehicle-ness + specific sailboat-ness

Object-oriented terminology

An abstract object description is a class

A single concrete object is an instance.

An instance stores its data in instance variables

The class functions are called methods.

... sometimes ...

Object-oriented terminology

So we'll say:

"We make an instance of a class."

"It has data." (instance variables)

"It has functions." (methods)

Object-oriented programming and images

What's in the set of image object properties?

     Pixel width
     Pixel height
     Number of channels
          grey values, RGB, RGBA (RGB with matte)

What are the functions of the image object?

     Read an image file
     Write an image file
     Get a pixel value
     Set a pixel value

Programming as problem modeling

Choose objects that make sense for the problem to be solved.

(Sounds like engineering...)

Programming as artistic modeling

Choose objects that enhance your ability to explore artistic possibilities.

(These objects may having nothing to do with engineering...)

Objects?