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Newsgroups: comp.lang.ada
Date: Fri, 17 Nov 2017 07:36:11 -0800 (PST)
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Subject: Re: Tests in a software release
From: Shark8 <onewingedshark@gmail.com>
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Xref: feeder.eternal-september.org comp.lang.ada:48962
Date: 2017-11-17T07:36:11-08:00
List-Id: <comp.lang.ada>

On Wednesday, November 15, 2017 at 1:46:35 PM UTC-7, Dmitry A. Kazakov wrote:
> On 2017-11-15 18:57, G. B. wrote:
> 
> > The most important thing is, designing by contract
> > is *not* programming defensively.
> 
> It exactly is. In both cases no assumptions beyond known preconditions 
> are made. Ada was especially designed to uphold defensive programming. 
> E.g. case requires others alternative:
> 
>     I : Positive := 1;
> 
>     case I is
>        when 1 =>
>           ...
>        when others => -- Defensive and mandatory
>           ...
>     end case;

Except that Ada allows CASE to be non-defensive and natural operation over sets:

Example : Integer with Import, Address => SOME_PORT;

Subtype Negative is Integer range Integer'First..Integer'Pred(Natural'First);
Subtype Small_Prime is Positive range Positive'Succ(Positive'First)..2**5
  with Static_Predicate => Small_Prime in
       2 | 3 | 5 | 7 | 11 | 13 | 17 | 19 | 23 | 29 | 31;

Case Example is
  when Negative    => Do_Negative;
  when 0           => Do_Zero;
  when 1           => Do_One;
  when Small_Prime => Do_Prime;
  when others      => Do_Positive_General;
End Case;