Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!samsung!usc!snorkelwacker!bloom-beacon!eru!luth!sunic!mcsun!ukc!reading!cf-cm!cf-cm!ted
From: ted@cf-cm.cm.cf.ac.uk (Ted Lawson)
Newsgroups: comp.lang.eiffel
Subject: Re: Rename/Redefine Table is Incorrect ?
Message-ID: <1990Mar12.213952.18467@computing-maths.cardiff.ac.uk>
Date: 12 Mar 90 21:39:52 GMT
References: <1190@cf-cm.UUCP> <2671@castle.ed.ac.uk> <266@eiffel.UUCP>
Sender: news@computing-maths.cardiff.ac.uk (Network News System)
Reply-To: ted@cf.cm.ac.uk (Ted Lawson)
Organization: University of Wales College of Cardiff, Cardiff, WALES, UK.
Lines: 39

In article <266@eiffel.UUCP> bertrand@eiffel.UUCP (Bertrand Meyer) writes:
><1190@cf-cm.UUCP> by ted@computing-maths.cardiff.ac.uk (Ted Lawson) writes:
>>>  One entry in the rename/redefine table on page 155 of
>>>  Eiffel: The Language (page 260 of OOSC) appears to be incorrect.
>>>
>>>  Case 6 of the table claims that
>>>
>>>      rename old as new
>>>      redefine old, new
>>>
>>>  causes b.old to bind to the same feature as c.new.
>
> I would like to state that Case 6 is correct
>to all the extent of my knowledge. (It is apparently counter-intuitive
>since this is not the first time it has been reported to me as being
>incorrect.)
>
>    When checking, however, I realized to my horror that our
>current implementation does not agree with the table for Case 6.
>This will be corrected shortly. Our apologies for this bug. 
>
>-- Bertrand Meyer

	Not only is case 6 counter-intuitive (in relation to case 4)
	it also seems rather messy to implement (as your implementer
	has discovered !). Well, until now no one has reported the "bug"
	so why not leave the implementation alone and just correct the
	documentation at the next opportunity ( :-) /2).

	Alternatively, could you explain the reasoning behind case 6's
	behaviour as documented. The only defense that I've seen of this
	was Kai Ng's posting here in March '89 - and that wasn't so
	much a defense as a rather intricate calculus for determining
	what the true binding was in each case.

	Ted Lawson

	ted%cm.cf.ac.uk@nsfnet-relay.ac.uk
	ted@uk.ac.cf.cm