Re: Numerical calculations: Why not use fixed point types for everything?

[Ada novice <shai.lesh@gmx.com>]

On Sunday, February 3, 2013 5:05:22 AM UTC+1, Shark8 wrote:
> 
> 
>     Type P is delta 0.1 digits 3 range 0.0..10.0;
> 
>     
> 
>     declare
> 
> 	Index : P := P'First;
> 
>     begin
> 
> 	loop
> 
> 	    Ada.Text_IO.Put_Line( Index'Img );
> 
> 	    Exit when Index = P'Last;
> 
> 	    Index:= P'Succ(Index);
> 
> 	End loop;
> 
>     end;
> 

I was working an example based on the working code you gave:

with Ada.Text_IO;
with Ada.Long_Float_Text_IO;

procedure Test is

type P is delta 0.1 digits 3 range 0.0..10.0;

        Index: P := P'First;
        Number   : Long_Float := 100.0;


   begin
      loop
         Ada.Text_IO.Put(Index'Img);Ada.Text_IO.Put("  ");

         Ada.Long_Float_Text_IO.Put (Item => Long_Float(Index)*Number, Fore => 3, Aft  => 3, Exp  => 0);Ada.Text_IO.Put("  ");

         --Number := Long_Float(Index)*Number;
         Ada.Long_Float_Text_IO.Put (Item => Number, Fore => 3, Aft  => 3, Exp  => 0);

         Ada.Text_IO.New_Line;

         exit when Index = P'Last;

         Index := P'Succ(Index);


      end loop;

end Test;


On running I get:

 0.0    0.000  100.000
 0.1   10.000  100.000
 0.2   20.000  100.000
 0.3   30.000  100.000
 0.4   40.000  100.000
 0.5   50.000  100.000
... and so on

which is expected.

Now, when I un-comment the line 

--Number := Long_Float(Index)*Number;

and run the code again, I get:

 0.0    0.000    0.000
 0.1    0.000    0.000
 0.2    0.000    0.000
 0.3    0.000    0.000
 0.4    0.000    0.000
 0.5    0.000    0.000

... and so on.

This is a weird behaviour. Why are the second and third columns all zeros now?

Thanks.
YC