Re: Why is Object Oriented so successfull



S Perryman wrote:
topmind wrote:

S Perryman wrote:

DK>The question wether programming with ADTs or programming with sets of ADTs
DK>(polymorphism falls here) is essential to OOP is open. However moving up
DK>abstraction levels obviously requires the latter.

Type substitutability is what OOP (Simula) brought to the game (via
inheritance) . Type substitutability is a good means of implementing the
Open-Closed Principle, solving all the grief of the "variant record"
problem (coupling etc) .

What "variant record problem"?

I've asked for this in the past

The "issue" of :

1. having a set of related entities, all/some having the same
properties, and each having properties specific to itself. Users of
the entities may wish to reference instances of the set as an entity
that has properties in common, or as the specific entity type.

2. changing the properties of any member of the
set, without affecting/impacting the other members (interface, impl) .

3. changing the representations (impls) of any member of the
set, without affecting/impacting the other members (interface, impl) .

4. changing the code written by users of the entity set, whenever the
members of the set changes.

5. correctness (being able to confirm the attempted use of properties
that do or do not belong to members of the set) .


All of these issues are known to experienced developers having faced
the variant record problem.

Similarly, said developers know that various programming paradigms/
langs can solve some of the problems, but not all. Type substitutability
(when used with other constructs/techniques) allows all of them to be
resolved.


> but nobody shown a practical example

Strange. Because "practical examples" are so easy to define.
And a basic example exists in a book you have so often claimed to debunk.

Then it should be easy for you to bring one up without fuss or muss.


If you understand or have experienced the variant record problem, you
should be able to define your own example in moments.

Not if its a figment of an OO author's imagination only.


Similarly you should be able to explain why/how 1-5 can/cannot be
resolved with various programming paradigms/constructs/techniques.


Regards,
Steven Perryman

-T-
oop.ismad.com
.

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