From mboxrd@z Thu Jan  1 00:00:00 1970
X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me
X-Spam-Level: 
X-Spam-Status: No, score=-0.9 required=5.0 tests=BAYES_00,FORGED_GMAIL_RCVD,
	FREEMAIL_FROM autolearn=no autolearn_force=no version=3.4.4
Path: 
 eternal-september.org!reader01.eternal-september.org!reader02.eternal-september.org!news.eternal-september.org!news.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail
From: Natasha Kerensikova <lithiumcat@gmail.com>
Newsgroups: comp.lang.ada
Subject: How to round to the nearest fixed-point value?
Date: Wed, 22 Jan 2014 16:48:26 +0000 (UTC)
Organization: A noiseless patient Spider
Message-ID: <slrnldvtim.1lme.lithiumcat@sigil.instinctive.eu>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
Injection-Date: Wed, 22 Jan 2014 16:48:26 +0000 (UTC)
Injection-Info: mx05.eternal-september.org;
 posting-host="31d6bde745a337034b005384ef225743";
	logging-data="16347"; mail-complaints-to="abuse@eternal-september.org";
	posting-account="U2FsdGVkX181ymPMJ2qWBYm7M+wRH17E"
User-Agent: slrn/0.9.9p1 (FreeBSD)
Cancel-Lock: sha1:ProzmazTZVMBvS/WeZGRT6P4tf0=
Xref: news.eternal-september.org comp.lang.ada:18248
Date: 2014-01-22T16:48:26+00:00
List-Id: <comp.lang.ada>

Hello,

from what I understood of the LRM (at least in Ada 2005 mode),
Fixed_Point_Type'Round is supposed to be a function returning a
Fixed_Point_Type value closest to its argument.

So I'm a bit surprised by the behavior of the following code:


package Lib is
   type High is delta 0.001 digits 9;
   type Low is delta 0.01 digits 9;

   function Convert (Value : High) return Low;
end Lib;


package body Lib is

   function Convert (Value : High) return Low is
   begin
      return Low'Round (Value);
   end Convert;

end Lib;


with Ada.Text_IO;
with Lib;

procedure Testcase is
   Raw_Value : constant Lib.High := 0.999;
   Shown_Value : Lib.Low;
begin
   Ada.Text_IO.Put_Line (Lib.Low'Image (Lib.Low'Round (Raw_Value)));
   Shown_Value := Lib.Convert (Raw_Value);
   Ada.Text_IO.Put_Line (Lib.Low'Image (Shown_Value));
end Testcase;



I tried building it with gnat 4.6.3 from debian stable kfreebsd and with
gnat-aux 4.7.3 from FreeBSD ports, and in both situations I got the
following output:
 1.00
 0.99


Is there something I'm doing wrong that would trigger the truncation at
some point? Or is this a compiler bug? Would anyone know a workaround to
get correct results?


Thanks in advance for your help,
Natasha