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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Subject: Re: Fixed point constants issue
Newsgroups: comp.lang.ada
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References: <op.vizer4qnd20q5n@jellix.jlfencey.com>
Date: Mon, 13 Sep 2010 20:04:32 +0200
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Date: 2010-09-13T20:04:31+02:00
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On Mon, 13 Sep 2010 19:27:30 +0200, Vinzent Hoefler wrote:

> Is this a GNAT bug or am I just stupid?
> 
> Suppose we have a fixed point type (with a rather large delta):
> 
> -- 8< --
> with Ada.Text_IO; use Ada.Text_IO;
> 
> procedure Fixed_Point
> is
>     FEET_PER_METER : constant := 0.3048;
>     HEIGHT         : constant := 10; -- Feet
>
>    type Altitude is delta (2.0**15 / 50_000.0) range 0.0 .. 50_000.0;

[...]  
> Can anyone shed some light on this? This has driven us crazy for weeks now.
> 
> [1] Of course, "Altitude'(HEIGHT * FEET_PER_METER)" yields "0.0" again.
>      At least this is consistent with my understanding so far.

Hmm, what did you expect? 0.3048 (FEET_PER_METER) is 0 when Altitude. That
is because 2.0**15/50_000.0=0.65536 > 0.3048.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de