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=-1.3 required=5.0 tests=BAYES_00,INVALID_MSGID
	autolearn=no autolearn_force=no version=3.4.4
X-Google-Language: ENGLISH,ASCII-7-bit
X-Google-Thread: 103376,c83229a21d53b2b3
X-Google-Attributes: gid103376,public
From: Al Christians <achrist@easystreet.com>
Subject: Re: Long Float Error from Gnat
Date: 1998/10/30
Message-ID: <363A49F3.DB0A0196@easystreet.com>#1/1
X-Deja-AN: 406831971
Content-Transfer-Encoding: 7bit
References: <3638F49C.E90A401E@easystreet.com> <uaf2ej591.fsf@gsfc.nasa.gov>
Content-Type: text/plain; charset=us-ascii
X-Trace: news6.ispnews.com 909789080 206.103.35.35 (Fri,
 30 Oct 1998 18:11:20 EDT)
Organization: Trillium Resources Corporation
MIME-Version: 1.0
NNTP-Posting-Date: Fri, 30 Oct 1998 18:11:20 EDT
Newsgroups: comp.lang.ada
Date: 1998-10-30T00:00:00+00:00
List-Id: <comp.lang.ada>

The problem is a little stranger than previously presented.  The 
program below will generate lots of errors with other values of
aft than 9.  The errors all seem to occur when the negative of the
exponent plus the digits after the decimal equals 41.  Wow!

Al

------------------------------------------------------------------------------

with Ada.Text_Io;
with Ada.Long_Float_Text_Io;
with Ada.Numerics.Long_Elementary_Functions;
with Ada.Numerics.Float_Random;
procedure Numeric_Test is

   The_Generator:  Ada.Numerics.Float_Random.Generator;

   function Generate_Random_Number return Long_Float is
   x:   Long_Float;
   begin
      X := Long_Float( Ada.Numerics.Float_Random.Random( The_Generator )
);
      X := X * 300.0 - 150.0;
      return Ada.Numerics.Long_Elementary_Functions.exp( X );
   end;


   Number_Of_Tests:   Natural := 1_000_000;
   X:       Long_Float;
   Y:       Long_Float;
   Count:   Integer  := 0;
   X_String,
   Y_String:   String(1..30);
   Last_Pos:   Natural;
   Largest:    Long_Float := -99.99E+99;
   Smallest:   Long_Float := +99.99E+99;

begin
   for I in 1..Number_Of_Tests loop
      X := Generate_Random_Number;
         for Digits_Aft in 6..12 loop
            begin
               Ada.Long_Float_Text_Io.Put( X_String, X, Aft =>
Digits_Aft );
               Ada.Long_Float_Text_Io.Get( X_String, Y, Last_Pos );
               Ada.Long_Float_Text_Io.Put( Y_String, Y, Aft =>
Digits_Aft );
               if  X_String /= Y_String then
                  Ada.Text_Io.Put( "Aft =>" & Integer'Image( Digits_Aft
) );
                  Ada.Text_Io.Put( Long_Float'Image(X) );
                  Ada.Text_Io.Put( "   ");
                  Ada.Text_Io.Put( Long_Float'Image(Y) );
                  Ada.Text_Io.New_Line;
                  if  x > Largest then
                     Largest := X;
                  end if;
                  if  x < Smallest then
                     Smallest := X;
                  end if;
                  Count := Count + 1;
               end if;
            exception
               when others =>
                  Ada.Text_Io.Put( "Exception:" & Long_Float'Image(X) );
                  Ada.Text_Io.Put( "   Aft:" & Integer'Image(Digits_Aft)
);
            end;
      end loop;
   end loop;
   Ada.Text_IO.Put_Line( "Largest:  " & Long_Float'Image(Largest) );
   Ada.Text_IO.Put_Line( "Smallest: " & Long_Float'Image(Smallest) );
   Ada.Text_IO.Put_Line( "Count:    " & Integer'Image(Count) );
end Numeric_Test;