Re: Interesting but sensitive topic to discuss (HELP: - OOP and CASE t

[pcg@aber.ac.uk (Piercarlo Grandi)]

>>> "jhd" == Joachim Durchholz <jhd@herold.franken.de> writes:

>>>> Could anybody post a short characterisation of prototype languages?

>> Basically, instead of creating a class, we instead create a blank
>> object and insert methods into it. Any object of that 'type' is a kind
>> of clone of that prototype object.

jhd> Hum, I think this description applies to class-based languages as
jhd> well.  Just say 'class' instead of 'blank prototype object'.

Not quite -- for one can then change one of those clones and make it
into a prototype for a new kind of objects, something which is quite not
possible in class based systems.  Also note that the prototype need not
be ``blank'' at all.

Also, if procedures belong _to_ objects instead of encapsulated _in_
classes, it becomes fairly natural to do reuse not quite by defining a
class by mixing in it procedures from other classes, but by forwarding
operations from one object to another, which need not be its prototype;
thus it is fairly natural to use delegation rather than inheritance in
prototype systems (even if the 'clone of' relationship can be used as if
it were an inheritance like relationship).

  An example is that if a trait of a prototype is declared irrevocably
  immutable, there is no need to duplicate it in every clone of that
  prototype object; it and all its clones can ``share'' that trait. The
  net effect is that then the implementation starts to resemble very
  much that of a class based system.

jhd> When are the methods inserted - at run-time?

Could well be, but not necessarily.

jhd> Then there's a real difference, [ ... ]

Not quite, for there are systems where classes can also be changed at
runtime