NetNews Usenet Archive 1992 #19/NN_1992_19.iso/spool/comp/object/3388

Text File | 1992-09-02 | 1.6 KB | 36 lines

Newsgroups: comp.object
Path: sparky!uunet!gossip.pyramid.com!decwrl!csus.edu!netcom.com!objsys
From: Bob Hathaway <[e-mail]>
Subject: Re: Object-Oriented Methodologies - Class Specifications
Message-ID: <[e-mail]>
Date: Wed, 02 Sep 92 19:57:03 GMT
Organization: Object Systems
References: <[e-mail]> <[e-mail]> <[e-mail]>
Lines: 25

  [Please forgive my brief interjection, I haven't been following.]

In article <[e-mail]> [e-mail] (Michael Wirth) writes:
>It's very interesting to note how our use of language (both programming and
>human) influences our thinking.  In particular, use of a message passing style
>of OOP, where methods are "owned" by their target class, leads to the curious
>asymmetry noted above.  In a language, CLOS, which uses generic functions and
>multi-methods (i.e., which specialize on more than one argument), this
>asymmetry can be avoided, i.e., we would define a generic function, INTERSECT,
>which would specialize on both its arguments.  One specific method which it
>would be useful to define then would specialize on lines and circles:
>        INTERSECT((x, LINE) (y, CIRCLE))

In "OOP" the INTERSECT function could be made a "friend" of LINE and CIRCLE
granting INTERSECT access to both classes without violating a strong form of
encapsulation.  Perhaps "strict OO messaging" could be substituted for "OOP".
But I'd keep in mind that such implementation access isn't always a good thing.

>Who "owns" this method?  Probably some higher level entity, like the "geometry
>package".

I agree.

bob
[e-mail]