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Newsgroups: comp.lang.ada
Subject: Re: Range excluding 0.0
From: csampson@inetworld.net (Charles H. Sampson)
Date: Sun, 30 Aug 2009 11:34:00 -0700
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Date: 2009-08-30T11:34:00-07:00
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Dmitry A. Kazakov <mailbox@dmitry-kazakov.de> wrote:

> On Sat, 29 Aug 2009 10:47:17 -0700, I wrote:
> 
> >      This is not just theoretical musing.  I currently work in the world
> > of compasses, so a range of the form [0.0 .. 360.0) is quite natural.
> > (That notation is neither mathematical nor Ada.  I hope its meaning is
> > clear.)
> 
> That is not range, the type would be not of real numbers. For example:
> 
>    340.0 + 25.0 = 5.0
>  
     Right, but that's not unusual.  Of the predefined types of Ada,
only modular and enumeration types are closed under their predefined
operations.

     What I want is a way to express the set of real numbers (in the Ada
sense) that an object of the type can legally hold.  We already write
the code to prevent a stored value of 360.0.  What I want is a
constraint error just in case we foul up.

     To be frank, I had forgotten that we can achieve the effect by
using Pred or some other attributes, even though I've done that in
another context.  But my question essentially was, why weren't we given
a notation to do it directly and easily?

                        Charlie
-- 
All the world's a stage, and most 
of us are desperately unrehearsed.  Sean O'Casey