From: mheaney@ni.net (Matthew Heaney)
Subject: Re: Design By Contract
Date: 1997/09/05
Date: 1997-09-05T00:00:00+00:00 [thread overview]
Message-ID: <mheaney-ya023680000509970830110001@news.ni.net> (raw)
In-Reply-To: EG0rp7.GtL@syd.csa.com.au
In article <EG0rp7.GtL@syd.csa.com.au>, nospam@thanks.com.au wrote:
>One obvious weakness of Ada child packages compared with Eiffel selective
>export is a lack of symmetry. With selective export, two modules can
>selectively export to each other. It's difficult to imagine how you could do
>this elegantly with child packages, if at all.
>
>It may be necessary in Ada to co-encapsulate under such circumstances. In
>that case, you lose the ability to control how each object updates the other's
>state.
This issue is frequently debated on comp.lang.ada, but I'll mention it
again. The _reason_ modules and types are orthogonal is precisely so you
can co-encapsulate types in the same package; this is why no "friend"
instruction is needed in Ada. If two types need access to each other's
state, then they are highly cohesive abstractions, and _should_ go in the
same package.
The argument that by using this idiom one "loses the ability to control how
each object updates each other's state" isn't an issue in real programs.
If such control were an issue, then perhaps the reason is that the
abstractions are too large or complex.
See John Volan's discussion about Ada's with'ing problem:
<http://bluemarble.net/~jvolan/WithingProblem/FAQ.html>
--------------------------------------------------------------------
Matthew Heaney
Software Development Consultant
<mailto:matthew_heaney@acm.org>
(818) 985-1271
next prev parent reply other threads:[~1997-09-05 0:00 UTC|newest]
Thread overview: 106+ messages / expand[flat|nested] mbox.gz Atom feed top
1997-08-21 0:00 Critique of Ariane 5 paper (finally!) aek
[not found] ` <33FC66AD.9A0799D4@calfp.co.uk>
1997-08-22 0:00 ` Robert S. White
1997-08-22 0:00 ` Samuel Mize
1997-08-22 0:00 ` Samuel Mize
1997-08-23 0:00 ` Ken Garlington
[not found] ` <33FFA4B1.3543@flash.net>
1997-08-26 0:00 ` Nick Leaton
[not found] ` <3403940F.4154@pseserv3.fw.hac.com>
1997-08-27 0:00 ` Design By Contract Ted Velkoff
[not found] ` <5u3c6v$gtf$2@miranda.gmrc.gecm.com>
[not found] ` <34058808.3BF@pseserv3.fw.hac.com>
1997-08-28 0:00 ` Darren New
1997-08-28 0:00 ` Patrick Doyle
1997-09-06 0:00 ` Joachim Durchholz
1997-09-06 0:00 ` Patrick Doyle
[not found] ` <JSA.97Aug27180328@alexandria.organon.com>
1997-08-28 0:00 ` W. Wesley Groleau x4923
1997-09-03 0:00 ` Don Harrison
1997-09-03 0:00 ` Jon S Anthony
1997-09-04 0:00 ` Don Harrison
[not found] ` <EFM140.Fy9@syd.csa.com.au>
1997-08-28 0:00 ` Jon S Anthony
1997-08-29 0:00 ` Don Harrison
1997-08-29 0:00 ` Jon S Anthony
[not found] ` <EFqE8L.4Eq@ecf.toronto.edu>
[not found] ` <JSA.97Aug30145058@alexandria.organon.com>
1997-09-01 0:00 ` Patrick Doyle
1997-09-02 0:00 ` Don Harrison
1997-09-02 0:00 ` Joerg Rodemann
1997-09-02 0:00 ` Jon S Anthony
1997-09-02 0:00 ` Jon S Anthony
1997-09-03 0:00 ` Don Harrison
[not found] ` <JSA.97Sep3201329@alexandria.organon.com>
1997-09-04 0:00 ` Paul Johnson
1997-09-05 0:00 ` Jon S Anthony
1997-09-08 0:00 ` Nick Leaton
1997-09-08 0:00 ` Matthew Heaney
1997-09-09 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 ` 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 ` Paul Johnson
1997-09-10 0:00 ` Matthew Heaney
1997-09-10 0:00 ` Darren New
1997-09-10 0:00 ` Robert Dewar
1997-09-12 0:00 ` Paul Johnson
1997-09-14 0:00 ` Robert Dewar
1997-09-14 0:00 ` Robert Dewar
1997-09-15 0:00 ` John G. Volan
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
1997-09-09 0:00 ` W. Wesley Groleau x4923
1997-09-09 0:00 ` Veli-Pekka Nousiainen
1997-09-09 0:00 ` Jon S Anthony
1997-09-09 0:00 ` Veli-Pekka Nousiainen
[not found] ` <EFzLn7.481@ecf.toronto.edu>
1997-09-04 0:00 ` Design By Contract Jon S Anthony
[not found] ` <EFz0pD.E6n@syd.csa.com.au>
1997-09-05 0:00 ` W. Wesley Groleau x4923
1997-09-05 0:00 ` subjectivity W. Wesley Groleau x4923
1997-09-05 0:00 ` subjectivity Matthew Heaney
1997-09-10 0:00 ` subjectivity Don Harrison
1997-09-12 0:00 ` subjectivity Jon S Anthony
1997-09-16 0:00 ` subjectivity Don Harrison
1997-09-16 0:00 ` subjectivity Jon S Anthony
1997-09-10 0:00 ` subjectivity Don Harrison
1997-09-10 0:00 ` subjectivity W. Wesley Groleau x4923
1997-09-11 0:00 ` subjectivity Don Harrison
1997-09-10 0:00 ` subjectivity W. Wesley Groleau x4923
[not found] ` <JSA.97Sep4172912@alexandria.organon.com>
[not found] ` <EG0oz8.F6M@syd.csa.com.au>
[not found] ` <EG0rp7.GtL@syd.csa.com.au>
1997-09-05 0:00 ` Matthew Heaney [this message]
1997-09-05 0:00 ` Design By Contract Jon S Anthony
1997-09-05 0:00 ` Nick Leaton
1997-09-08 0:00 ` Jon S Anthony
1997-09-09 0:00 ` Nick Leaton
1997-09-10 0:00 ` Paul Johnson
1997-09-06 0:00 ` Patrick Doyle
1997-09-09 0:00 ` Robert A Duff
1997-09-09 0:00 ` Matthew Heaney
1997-08-29 0:00 ` Patrick Doyle
1997-08-29 0:00 ` Jon S Anthony
[not found] ` <EFqDw0.3x7@ecf.toronto.edu>
[not found] ` <JSA.97Aug30145354@alexandria.organon.com>
1997-09-01 0:00 ` Patrick Doyle
1997-08-28 0:00 ` Robert Dewar
1997-08-29 0:00 ` Don Harrison
[not found] ` <349224633wnr@eiffel.demon.co.uk>
1997-08-27 0:00 ` Design by Contract Robert Dewar
1997-08-29 0:00 ` Don Harrison
[not found] ` <3406BEF7.2FC3@flash.net>
[not found] ` <3406E0F7.6FF7ED99@calfp.co.uk>
1997-09-02 0:00 ` Critique of Ariane 5 paper (finally!) Ken Garlington
[not found] <5u1627$1fak@info4.rus.uni-stuttgart.de>
[not found] ` <EFM1Lx.GD2@syd.csa.com.au>
1997-08-28 0:00 ` Design by Contract Robert Dewar
-- strict thread matches above, loose matches on Subject: below --
1997-08-07 0:00 Safety-critical development in Ada and Eiffel Ken Garlington
1997-08-12 0:00 ` Don Harrison
1997-08-12 0:00 ` Jon S Anthony
1997-08-13 0:00 ` Ted Velkoff
1997-08-13 0:00 ` Ken Garlington
1997-08-14 0:00 ` Nick Leaton
1997-08-18 0:00 ` Joachim Durchholz
1997-08-19 0:00 ` Ken Garlington
1997-08-21 0:00 ` Joachim Durchholz
1997-08-23 0:00 ` Ken Garlington
[not found] ` <JSA.97Aug25181856@alexandria.organon.com>
[not found] ` <34023A1F.41C67EA6@eiffel.com>
1997-08-25 0:00 ` Design by Contract Bertrand Meyer
1997-08-25 0:00 ` Bertrand Meyer
[not found] ` <3402d123.0@news.uni-ulm.de>
1997-08-26 0:00 ` Nick Leaton
[not found] ` <3402e51d.0@news.uni-ulm.de>
[not found] ` <3402E8C9.3384D976@calfp.co.uk>
[not found] ` <dewar.872631036@merv>
1997-08-27 0:00 ` Ted Velkoff
1997-08-27 0:00 ` Matt Kennel (Remove 'NOSPAM' to reply)
[not found] ` <34050F3C.5A3A@invest.amp.com.au>
1997-08-28 0:00 ` Robert Dewar
1997-08-29 0:00 ` Paul Johnson
1997-08-31 0:00 ` Matt Kennel (Remove 'NOSPAM' to reply)
1997-09-01 0:00 ` John F. Bell III
1997-09-02 0:00 ` Ken Garlington
1997-09-05 0:00 ` Robert Dewar
[not found] ` <dewar.872887402@merv>
1997-09-02 0:00 ` Ken Garlington
1997-09-03 0:00 ` Thomas Beale
[not found] ` <EFxx8q.2sw@ecf.toronto.edu>
1997-09-04 0:00 ` Thomas Beale
1997-09-05 0:00 ` Robert Dewar
1997-09-05 0:00 ` Ken Garlington
[not found] ` <340306E1.5FB64D70@XYZZYcalfp.com>
1997-08-28 0:00 ` Mark Bennison
[not found] ` <bengtk-2708972209500001@sl35.modempool.kth.se>
1997-08-28 0:00 ` Nick Leaton
1997-08-25 0:00 ` Bertrand Meyer
[not found] ` <JSA.97Aug26151833@alexandria.organon.com>
1997-08-27 0:00 ` Patrick Doyle
1997-08-25 0:00 ` Bertrand Meyer
1997-08-25 0:00 ` Steve Stringfellow
1997-08-26 0:00 ` Don Harrison
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