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From: pw@tnoibbc.UUCP (Peter Willems)
Newsgroups: comp.lang.eiffel
Subject: Re: Suggestion for use of Void
Summary: Class NONE as solution.
Message-ID: <2195@tnoibbc.UUCP>
Date: 4 Dec 90 22:04:25 GMT
References: <1037@tetrauk.UUCP> <4106@tantalum.UUCP>
Lines: 21


>In article <1037@tetrauk.UUCP> rick@tetrauk.UUCP (Rick Jones) writes:
>>A Void of course conforms to any class type, so it is syntactically valid
>>anywhere an object reference is required.
>>
>>This raises the interesting issue of forms such as:
>>	obj_ref := Void			equivalent to	obj_ref.Forget
>>	if obj_ref = Void then		equivalent to	if obj_ref.Void then

I seem to remember that Bertrand Meyer introduced for this same issue
the idea of a class NONE.  Conceptually class NONE inherits from all other
classes and therefore conforms to any class type.  Of course there is no
real difference with the Void concept, it is slightly more elegant I think.

Probably this enhancement will be part of Eiffel 3.0.

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