From: "Mark L. Fussell" <mark.fussell@chimu.com>
Subject: Re: Building blocks (Was: Design By Contract)
Date: 1997/09/19
Date: 1997-09-19T00:00:00+00:00 [thread overview]
Message-ID: <34228047.65E8@chimu.com> (raw)
In-Reply-To: 11861963wnr@eiffel.demon.co.uk
The following extracts salient thread pieces from Paul Johnson, Stephen
Leake, Roger Browne, and myself.
> > Paul Johnson wrote:
> > > Ada allows the programmer to quietly ignore an exception and pretend
> > > that a routine succeeded when in fact it failed. This is wrong.
Mark L. Fussell <mark.fussell@chimu.com> writes:
[SNIPPED Eiffel Equivalent of Ada Exception]
> > The functionality [of the Eiffel version]
> > is identical to the Ada version, so it likewise
> > "pretends to succeed when in fact it failed". The important thing to
> > Bertrand Meyer [from my understanding] is that ONLY the main body can
> > exit a routine without exception...
Roger Browne wrote:
> ..and therefore it must meet the postcondition of that routine, else
> it triggers a further exception (a "routine failure" exception).
>
> So, to the extent that the contract can be coded into the postcondition,
> this example does not "pretend to succeed when in fact it failed".
And the Ada and Eiffel examples are equivalent from the caller's point
of view: exactly the same state was reached when the routine returns.
So we have refuted the concept that Ada routines are "flawed" and can
'pretend to succeed' (via "ignoring" exceptions) where Eiffel routines
can not. Either both succeeded or both failed. Either both can pretend
to succeed (by not throwing an exception when the contract is not
fulfilled) or neither can.
Two differences are (1) Eiffel has postconditions and could better
(automatically) recognize failure which would reduce 'pretending'. And
(2) the feel of the code is different, possibly leading to focusing more
on fulfilling the contract and recognizing when you can not. These may
be good (even superior) things in Eiffel but they don't make Ada's
exception mechanism "wrong" or flawed.
--Mark
mark.fussell@chimu.com
i ChiMu Corporation Architectures for Information
h M info@chimu.com Object-Oriented Information Systems
C u www.chimu.com Architecture, Frameworks, and Mentoring
next prev parent reply other threads:[~1997-09-19 0:00 UTC|newest]
Thread overview: 74+ messages / expand[flat|nested] mbox.gz Atom feed top
1997-09-09 0:00 Building blocks (Was: Design By Contract) Marc Wachowitz
1997-09-15 0:00 ` Joachim Durchholz
1997-09-17 0:00 ` Paul Johnson
1997-09-18 0:00 ` Stephen Leake
1997-09-18 0:00 ` W. Wesley Groleau x4923
1997-09-21 0:00 ` Matthew Heaney
1997-09-18 0:00 ` Mark L. Fussell
1997-09-19 0:00 ` Robert A Duff
1997-09-20 0:00 ` Joachim Durchholz
1997-09-22 0:00 ` Matthew Heaney
1997-09-23 0:00 ` Joachim Durchholz
1997-09-23 0:00 ` Veli-Pekka Nousiainen
1997-10-03 0:00 ` Robert I. Eachus
1997-10-04 0:00 ` Paul Johnson
1997-10-14 0:00 ` Robert I. Eachus
1997-09-23 0:00 ` Jon S Anthony
1997-09-24 0:00 ` Richard A. O'Keefe
1997-09-24 0:00 ` Alan E & Carmel J Brain
1997-09-25 0:00 ` Anonymous
1997-09-30 0:00 ` Alan E & Carmel J Brain
1997-09-30 0:00 ` Matthew Heaney
1997-09-30 0:00 ` W. Wesley Groleau x4923
1997-09-30 0:00 ` Matthew Heaney
1997-10-01 0:00 ` Alan E & Carmel J Brain
1997-09-30 0:00 ` Neil Wilson
1997-09-30 0:00 ` Stephen Leake
1997-10-01 0:00 ` Anonymous
1997-10-01 0:00 ` Paul M Gover
1997-10-04 0:00 ` Paul Johnson
1997-10-04 0:00 ` Matthew Heaney
1997-10-15 0:00 ` Paul Johnson
1997-10-15 0:00 ` Matthew Heaney
1997-10-16 0:00 ` Joachim Durchholz
1997-10-17 0:00 ` Robert I. Eachus
1997-10-16 0:00 ` Joachim Durchholz
1997-10-22 0:00 ` Reimer Behrends
1997-10-01 0:00 ` Joachim Durchholz
1997-10-02 0:00 ` Robert A Duff
1997-10-02 0:00 ` Tucker Taft
1997-10-02 0:00 ` Matthew Heaney
1997-10-03 0:00 ` Stephen Leake
1997-10-04 0:00 ` Matthew Heaney
1997-10-07 0:00 ` Robert A Duff
[not found] ` <11861963wnr@eiffel.demon.co.uk>
1997-09-19 0:00 ` Mark L. Fussell [this message]
1997-09-19 0:00 ` Jon S Anthony
1997-09-23 0:00 ` Mark L. Fussell
1997-09-18 0:00 ` Jon S Anthony
1997-09-18 0:00 ` Robert Dewar
-- strict thread matches above, loose matches on Subject: below --
1997-09-11 0:00 Robert Dewar
1997-09-09 0:00 Marc Wachowitz
1997-09-02 0:00 Design By Contract Jon S Anthony
[not found] ` <JSA.97Sep3201329@alexandria.organon.com>
1997-09-04 0:00 ` Paul Johnson
[not found] ` <5un58u$9ih$1@gonzo.sun3.iaf.nl>
1997-09-06 0:00 ` Building blocks (Was: Design By Contract) Joachim Durchholz
1997-09-08 0:00 ` Paul Johnson
1997-09-08 0:00 ` Brian Rogoff
1997-09-09 0:00 ` Veli-Pekka Nousiainen
1997-09-09 0:00 ` Veli-Pekka Nousiainen
1997-09-09 0:00 ` Jon S Anthony
1997-09-09 0:00 ` W. Wesley Groleau x4923
1997-09-09 0:00 ` Matthew Heaney
1997-09-09 0:00 ` Brian Rogoff
1997-09-09 0:00 ` W. Wesley Groleau x4923
1997-09-10 0:00 ` Robert A Duff
1997-09-12 0:00 ` Jon S Anthony
1997-09-10 0:00 ` Robert Dewar
1997-09-12 0:00 ` Paul Johnson
1997-09-14 0:00 ` Robert Dewar
1997-09-15 0:00 ` John G. Volan
1997-09-14 0:00 ` Robert Dewar
1997-09-14 0:00 ` Robert Dewar
1997-09-12 0:00 ` Jon S Anthony
1997-09-12 0:00 ` Robert Dewar
1997-09-16 0:00 ` Brian Rogoff
1997-09-10 0:00 ` Paul Johnson
1997-09-10 0:00 ` Darren New
1997-09-10 0:00 ` Matthew Heaney
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