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From: "Jeffrey R. Carter" <spam.jrcarter.not@spam.not.acm.org>
Newsgroups: comp.lang.ada
Subject: Re: getting same output as gfortran, long_float
Date: Thu, 30 Apr 2015 18:16:52 -0700
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Date: 2015-04-30T18:16:52-07:00
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On 04/30/2015 03:32 PM, Nasser M. Abbasi wrote:
> 
> With Ada.Text_IO;
> with system;
> procedure Foo_However_Many is
>    type Big is digits System.Max_Digits;
>    X : Big  := 12.0 * 0.0001 / (1.0 * (1.0 - 0.1) ** 4);
> begin -- Foo_However_Many
>    Ada.Text_IO.Put_Line (Item => X'Img);
> end Foo_However_Many;
> 
> ./foo_however_many
>  1.82898948331047096E-03

You could always do

with Ada.Text_IO;
with PragmARC.Rational_Numbers;
with PragmARC.Unbounded_Integers;

procedure Foo_Rational is
   use PragmARC;

   use type Rational_Numbers.Rational;
   use type Unbounded_Integers.Unbounded_Integer;

   One_I  : constant Unbounded_Integers.Unbounded_Integer := +1;
   Twelve : constant Rational_Numbers.Rational := Unbounded_Integers."+" (12) /
One_I;
   P0001  : constant Rational_Numbers.Rational := One_I / (+10_000); -- 0.0001
   P1     : constant Rational_Numbers.Rational := One_I / (+10); -- 0.1

   One : Rational_Numbers.Rational renames Rational_Numbers.One;

   Result : constant Rational_Numbers.Rational := Twelve * P0001 / (One * (One -
P1) ** 4);
begin -- Foo_Rational
   Ada.Text_IO.Put_Line (Item => Rational_Numbers.Image (Result) );
end Foo_Rational;

$ gnatmake -gnatano -gnatwa -O2 -fstack-check -I../RAC foo_rational.adb
gcc-4.6 -c -gnatano -gnatwa -O2 -fstack-check -I../RAC foo_rational.adb
gnatbind -I../RAC -x foo_rational.ali
gnatlink foo_rational.ali -O2 -fstack-check
jrcarter@jcarter-singo-laptop:~/Code$ ./foo_rational
0.0018289894833104709647919524462734339277549154092363968907178783721993598536808413351623228166438042981252857796067672610882487425697302240512117055326931870141746684956561499771376314586191129401005944215820759030635573845450388660265203475080018289894833104709647919524462734339277549154092363968907178783721993598536808413351623228166438042981252857796067672610882487425697302240512117055326931870141746684956561499771376314586191129401005944215820759030635573845450388660265203475080018289894833104709647919524462734339277549154092363968907178783721993598536808413351623228166438042981252857796067672610882487425697302240512117055326931870141746684956561499771376314586191129401005944215820759030635573845450388660265203475080018289894833104709647919524462734339277549154092363968907178783721993598536808413351623228166438042981252857796067672610882487425697302240512117055326931870141746684956561499771376314586191129401005944215820759030635573845450388660265203475080018289894833104709647919

524462

The referenced PragmARC pkgs are available in the beta version of the PragmAda
Reusable Components available from

https://pragmada.x10hosting.com/pragmarc.htm

-- 
Jeff Carter
"Many times we're given rhymes that are quite unsingable."
Monty Python and the Holy Grail
57