Path: utzoo!attcan!uunet!mcsun!hp4nl!botter!star.cs.vu.nl!jos
From: jos@cs.vu.nl (Jos Warmer)
Newsgroups: comp.sw.components
Subject: Re: Inheritance vs. component efficienc
Message-ID: <3053@vlot.cs.vu.nl>
Date: 24 Aug 89 06:53:35 GMT
References: <5682@hubcap.clemson.edu> <130200005@p.cs.uiuc.edu> <1233@ttds.UUCP>
Organization: V.U. Informatica, Amsterdam, the Netherlands
Lines: 43

jonasn@ttds.UUCP (Jonas Nygren) writes:

>In article <130200005@p.cs.uiuc.edu> johnson@p.cs.uiuc.edu writes:
>>      2) For some reason, run-time binding is necessary.

>If C is to be considered a conventional language then there is a way to avoid
>the case-construct. Just declare a structure as follows:

>	typedef struct{
>		....
>		void (*display)();
>	} window;

>and then the following code would achieve what Ralph wants:

>	window a, b;

>	a.display = draw_small_window;
>	b.display = draw_big_window;

The previous two lines are just run-time binding done by hand.

>	(*a.display)(a);
>	(*b.display)(b);

>without case-constructs.

>It's even possible to achieve single-inheritance by adding the derived
>class's members after the base-class members in a new struct, and this
>could be semi-automated by nested include-files.

This is just inheritance done by hand.

Conclusion:

Run-time binding still seems neccesary.
OO languages offer this support automatically.
In C you can do-it-yourself, although it looks very cumbersome to me.

                                 Jos Warmer
				 jos@cs.vu.nl
				 ...uunet!mcvax!cs.vu.nl!jos
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