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From: adambeneschan@gmail.com
Subject: Re: How to round to the nearest fixed-point value?
Date: Wed, 22 Jan 2014 14:45:22 -0800 (PST)
Date: 2014-01-22T14:45:22-08:00	[thread overview]
Message-ID: <f37cea1f-6c68-483b-8097-cca566a5d8a2@googlegroups.com> (raw)
In-Reply-To: <slrnldvtim.1lme.lithiumcat@sigil.instinctive.eu>

On Wednesday, January 22, 2014 8:48:26 AM UTC-8, Natasha Kerensikova wrote:

> 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;

>  1.00
>  0.99

I'm pretty sure this is a compiler bug.  Since Low'Small is a multiple of High'Small, you can work around it by changing the definition of Convert to

    return Low (Value + Low'Small / 2);

(Low'Small is a universal real and therefore Low'Small/2 will be interpreted as a value of type High.  The type conversion to Low will truncate.)

                            -- Adam

  parent reply	other threads:[~2014-01-22 22:45 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-01-22 16:48 How to round to the nearest fixed-point value? Natasha Kerensikova
2014-01-22 17:53 ` G.B.
2014-01-22 22:26   ` adambeneschan
2014-01-23  9:21     ` Georg Bauhaus
2014-01-22 22:45 ` adambeneschan [this message]
2014-01-23  5:29   ` J-P. Rosen
2014-01-23  7:00     ` Natasha Kerensikova
2014-01-23  9:42     ` Georg Bauhaus
2014-01-23  7:02   ` Natasha Kerensikova
2014-01-23 16:41     ` adambeneschan
2014-01-24  9:58 ` Natasha Kerensikova
2014-01-24 22:30   ` Randy Brukardt
2014-01-24 22:47     ` Randy Brukardt
2014-01-26 14:19     ` Natasha Kerensikova
2014-01-28 23:43       ` Randy Brukardt
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