Path: utzoo!mnetor!uunet!husc6!cmcl2!nrl-cmf!ames!ptsfa!well!mitsu
From: mitsu@well.UUCP (Mitsuharu Hadeishi)
Newsgroups: comp.lang.c++
Subject: Re: generic types
Message-ID: <5028@well.UUCP>
Date: 18 Jan 88 19:19:39 GMT
References: <217@goofy.megatest.UUCP>
Reply-To: mitsu@well.UUCP (Mitsuharu Hadeishi)
Organization: Whole Earth 'Lectronic Link, Sausalito, CA
Lines: 34
Keywords: generic types class derived
Summary: The Book is woefully incomplete here


	We've developed a set of macros for deriving from generic classes
that allows full flexibility (and even a kind of multiple inheritance)
without causing the implementor to have to define a whole bunch of
macros.  The implementor simply defines the "body" of the class as a macro,
with possible parameters a type or two and a class name.  If the
programmer wishes to avoid having to specify a class name, s/he can use
the simplest macro "Declare()" (similar to the "declare()" macro in
The Book.)  Declare(), however, is defined in terms of a series of
ever-more precise macros which allow the programmer increasing flexibility.
The "body" macro is NOT a full class declaration, only the "body" of
the class (the member functions).  If the programmer wishes to
create his/her own class derived from the base class (say, "ListElement")
s/he can simply say

	class NameNode : public ListElement
		{
		char name[40];
		public:
		// ...
		Inherit(ListElement,NameNode);
		};

	This is appropriate for those generic classes that almost always
require the addition of data members to be useful (a linked list without
any data is pretty useless.)

	We've spent a long time arguing over the names, and have come up
with a fairly simple, standard convention.  Of course, all of this will
be rendered unnecessary when and if parameterized classes are introduced
into C++; however, we find it useful for our current needs.

				-Mitsu Hadeishi
				 Electronic Arts