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From: Nicholas Paul Collin Gloucester <Colin_Paul_Gloster@ACM.org>
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 comp.lang.eiffel,comp.lang.ada,comp.lang.modula3,comp.lang.pascal,comp.programming
Subject: Re: Alternatives to C: ObjectPascal, Eiffel, Ada or Modula-3?
Date: Mon, 20 Jul 2009 10:13:31 +0000 (UTC)
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Date: 2009-07-20T10:13:31+00:00
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On 2009-07-18, Pascal J. Bourguignon <pjb@informatimago.com> wrote:

|-----------------------------------------------------------------------------|
|"[..]                                                                        |
|                                                                             |
|Of those, I'd use Modula-3.                                                  |
|(you may also consider: Objective Modula-2)"                                 |
|-----------------------------------------------------------------------------|

This is the first I have heard of Objective Modula-2. Thank you.

Unfortunately, Wirthian languages tend to use structural equivalence
of types instead of occurrence equivalence, such as Modula-3 according
to
HTTP://web.archive.org/web/20051001044031/http://archive.dstc.edu.au/AU/staff/crawley/ada/m3-vs-ada.html#section4.1
and many interpretations of an early Pascal definition, so I suspect
that Modula-2 also had this weakness. The following excerpt from
HTTP://Objective.Modula2.net/
- "[..]
The base language is Modula-2 as defined by Niklaus Wirth in the
fourth edition of Programming in Modula-2 with the following omissions
and restrictions:

Omissions
[..]
* No subrange types
[..]" -
seems to indicate that it is even worse.

Ada allows you to choose for some types to be treated with occurrence
equivalence (called types in Ada:
WWW.AdaIC.org/standards/05rm/html/RM-3-2-1.html
) and for other types to be treated as
structurally equivalent (called subtypes in Ada:
WWW.AdaIC.org/standards/05rm/html/RM-3-2-2.html
) as you deem to be appropriate. Unlike for example Eiffel's Design by
Contract, this is not something which is activated or deactivated by a
compiler switch: a single Ada function can exploit both approaches at
the same time without being recompiled.

Regards,
Nicholas Paul Collin Gloucester