From: Dirk Herrmann <fight_spam@invalid.invalid>
Subject: Re: conversions between fixed-point types
Date: Sat, 26 Sep 2009 16:43:22 +0200
Date: 2009-09-26T16:43:22+02:00 [thread overview]
Message-ID: <h9l9aa$rb9$1@news.albasani.net> (raw)
In-Reply-To: <4abc8389$1_1@glkas0286.greenlnk.net>
Stuart wrote:
> Having played with this on GNATPro 6.1.2 (to PC target) it does report
> FpB'Machine_Rounds as false. It also rounds values like -1.59999 down to
> -1.2 (which is a logical consequence). Technically this is still within the
> error bounds declared for FpB (delta 0.4) so it is not "wrong" within the
> rules of the language definition. But it is very counter-intuitive and is
> the sort of thing I find frustrating.
>
> I also tested the problem on GreenHills AdaMULTI (4.2.3 to PowerPC target);
> this gave FpB'Machine_Rounds as true and gave the more intuitive results.
>
> -1.5 -> -1.6
> -1.40001 -> -1.6
> -1.4 -> -1.2
>
> So although there does look to be a language "gotcha" here, it depends upon
> the compiler's choice of 'Machine_Rounds.
Whom could I contact to figure out whether this is an omission in the language
definition (which could then be fixed) or whether it is intentional? I would
also like to ask about another issue:
Dirk Herrmann wrote:
> Robert A Duff wrote:
>> By the way, you can say:
>>
>> for T'Small use T'Delta;
>>
>> to avoid repeating yourself.
>
> I have tried that, especially since the very same recommendation was
> given in the Barnes book "Ada 2005". But, GNAT gives an error message.
> It seems that the very moment you reference T'Delta the type T gets
> "frozen" such that the "use" statement itself freezes T before it can
> modify it. I don't know if this is what the authors of the reference
> manual had intended, but GNAT interprets it that way.
--
Dirk
next prev parent reply other threads:[~2009-09-26 14:43 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-09-18 21:35 conversions between fixed-point types Dirk Herrmann
2009-09-18 22:42 ` Adam Beneschan
2009-09-19 12:41 ` Dirk Herrmann
2009-09-19 14:48 ` John B. Matthews
2009-09-20 8:15 ` Dirk Herrmann
2009-09-20 14:22 ` Robert A Duff
2009-09-20 18:55 ` Dirk Herrmann
2009-09-20 20:34 ` Simon Clubley
2009-09-23 20:46 ` Dirk Herrmann
2009-09-27 17:15 ` Simon Clubley
2009-09-27 19:22 ` sjw
2009-09-28 20:18 ` Dirk Herrmann
2009-09-28 18:37 ` Robert A Duff
2009-09-28 20:50 ` Dirk Herrmann
2009-09-20 15:18 ` John B. Matthews
2009-09-20 19:13 ` Dirk Herrmann
2009-09-20 20:09 ` tmoran
2009-09-21 17:24 ` Jeffrey R. Carter
2009-09-23 20:57 ` Dirk Herrmann
2009-09-23 22:28 ` Jeffrey R. Carter
2009-09-24 1:05 ` Adam Beneschan
2009-09-24 3:57 ` Jeffrey R. Carter
2009-09-25 8:47 ` Stuart
2009-09-25 20:41 ` sjw
2009-09-25 21:58 ` Jeffrey R. Carter
2009-09-28 13:40 ` Stuart
2009-09-26 14:43 ` Dirk Herrmann [this message]
2009-09-28 15:15 ` Adam Beneschan
2009-09-26 14:31 ` Dirk Herrmann
2009-09-19 18:38 ` tmoran
2009-09-20 8:22 ` sjw
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