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=-1.4 required=5.0 tests=BAYES_00,PDS_BTC_ID
	autolearn=no autolearn_force=no version=3.4.4
X-Google-Thread: 103376,1525d71e3169ed06
X-Google-Attributes: gid103376,public
X-Google-Language: ENGLISH,ASCII-7-bit
Path: 
 g2news1.google.com!news4.google.com!news2.google.com!fu-berlin.de!uni-berlin.de!individual.net!not-for-mail
From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: Float precision - gnat vs objectada
Date: Thu, 2 Dec 2004 09:32:41 +0100
Message-ID: <67y3zzucp3e1.uomux6epm0zs$.dlg@40tude.net>
References: <1c8dc73c.0412010746.272b978@posting.google.com>
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
X-Trace: individual.net M4oJWvlBsgk8b2xvTxPc0gZbENsOi/Be4/7V3JSmZmA6hXQ6M=
User-Agent: 40tude_Dialog/2.0.12.1
Xref: g2news1.google.com comp.lang.ada:6711
Date: 2004-12-02T09:32:41+01:00
List-Id: <comp.lang.ada>

On 1 Dec 2004 07:46:38 -0800, P Torle wrote:

> I'm working on a Ada95/C project that shall run on both Linux and
> Windows.
> I have some problems getting the same float precision on both
> platforms.

To get the same precision tell the compiler which one you need.

type My_Float is digits N;

> Example:
> -----------------------------
> subtype Real is Long_Float;
> pi : Real;
> 
> pi := 3.14159_26535_89793_23846_26433_83279_50288_41971_69399_37511;
> Real_Io.Put(pi, Aft => 25);
> -----------------------------
> 
> Results:
> Linux: 3.1415926535897931200000000E+00
> Win32: 3.1415926535897931159979634E+00
> 
> The thing is, the following float-precision definitions are equal on
> both Linux and Windows:
> 
> Real'Machine_Mantissa  : 53
> Real'Machine_Emin      : -1021
> Real'Machine_Emax      : 1024
> Real'Digits            : 15
> 
> So why the difference? 

Probably because the implementations of Real_IO.Put are slightly different.
But anything after 3.14159_26535_8979 is just a noise. The problem is not
whether Long_Floats are different or not. The problem is that Aft=>25 >
T'Digits.

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