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From: Niklas Holsti <niklas.holsti@tidorum.invalid>
Newsgroups: comp.lang.ada
Subject: Re: List of Negative Language rules?
Date: Sun, 05 Aug 2012 22:17:30 +0300
Organization: Tidorum Ltd
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Date: 2012-08-05T22:17:30+03:00
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On 12-08-05 18:24 , Bill Findlay wrote:
> On 05/08/2012 15:39, in article
> e6963165-d99c-4b35-be88-b9f7aa8d5f4a@googlegroups.com, "Patrick"
> <patrick@spellingbeewinnars.org> wrote:
> 
>>
>> Does anyone happen to know if there is a list of negative language rules? If
>> not I could try to re-read the book and compile a list. I think it would make
>> for a good cheat sheet to paste to the wall to avoid programming errors.
> 
> Trying to beat Dmitry to it: there is an infinity of negative rules.
> You would need to use Hilbert paper. 8-)
> 
> More seriously: have you seen the Ada Rationale?

Also, if you happen to wonder /why/ a certain negative rule exists, the
"Annotated" version of the Ada RM often explains it. For example, the
rule forbidding access parameters for task entries is explained in
http://www.ada-auth.org/standards/12aarm/html/AA-9-5-2.html (paragraphs
13a-13e). Unfortunately, to understand the explanation one often needs
to have a bit of language-lawyer background knowledge.

There are two common reasons for "negative" rules: (1) The forbidden
thing does not really make sense, or (2) It would be too difficult or
impossible to implement it efficiently (at least in the current compilers).

-- 
Niklas Holsti
Tidorum Ltd
niklas holsti tidorum fi
      .      @       .