Re: OOP considered snake oil

Xah Lee <xah@xahlee.org> writes about:


  The original Chinese snake oil indeed seems to have
  inflammation-reducing properties and thus might be a
  ?plausible remedy for joint pain? (Wikipedia).

  Then, even object-oriented programming might have something
  good? But, wait, what does ?object-oriented programming?
  actually mean?

  These are the questions I recently asked myself.
  My answers are following. Other answers are possible, too.
  Maybe someone wants to provide them.

                              ~~

  What is object-oriented programming?

    Object-oriented programming uses objects (storage entities)
    annotated with run-time types: Every object carries
    information about its type, which implies information about
    the layout and encoding of its storage.

  What is an object-oriented programming language?

    An object-oriented programming language supports
    object-oriented programming, but it usually hides the type
    information of objects and automatically assigns operations
    specified for a type to each object. Thus, in an object
    oriented programming language, the programmer does not read
    the type information himself nor does he use it to select an
    appropriate action. Instead he just states the action by a
    "verb" with a type and the programing language will then
    make sure, that the correct implementation is called for any
    given object at run-time. This is called ?run-time
    polymorphism? or ?late binding?. Individual object-oriented
    programming languages might include additional support for
    object-oriented programing, but this binding is the core
    feature of every object-oriented programming language.

  What is the main advantage of an object-oriented programming
  language?

    The main advantage is that verbs can be extended without the
    need to modify existing code. For example, in Java, a new
    type can extend the verb ?toString?. This extension can then
    be used immediatly by the existing ?println? verb, without
    the need that the author of the code for ?println? was aware
    of the new type, so it is not necessary to modify the given
    Java SE library, which contains other definitions of the
    verb ?toString?. One only needs to /add/ new code. Thus, the
    ?open/closed principle? is fulfilled.

  Can you give a small example programm that shows something
  that can be done in an object-oriented programming language,
  but is not possible in a purely procedural programming
  language?

    Yes, a Java program illustrating the answer to the previous
    question is:

class Position
{ int x; int y; public java.lang.String toString()
  { return java.lang.String.valueOf( x ) +
    ", " + java.lang.String.valufOf( y ); }}

public class Main
{ public static void main( final java.lang.String[] args )
  { java.lang.System.out.println( new Position() ); }}

    The output of this program is as follows.

0, 0

  What is the reason for run-time information?

    It is needed when ever data is to be transfered between to
    parties, whose encoding, layout or language might change or
    is not yet known, to indicate this encoding, layout or
    language.