Re: Hexadecimal and stream element arrays

["Jeffrey R. Carter" <ggsub@pragmada.x10hosting.com>]

On Apr 19, 1:52 pm, Ludovic Brenta <ludo...@ludovic-brenta.org> wrote:
>
> I find it funny you should say that because I thought exactly the
> opposite: letting Ada.Text_IO (which is notoriously slow) do the
> conversion to string and then doing string manipulation is less clear
> and more error-prone, IMHO (a proper implementation would use a simple,
> but full-fledged, finite state machine).  But your approach is certainly
> valid and correct nevertheless.

Funny you should say that ...

Considering that I can write

function Hex_Image (Number : Ada.Streams.Stream_Element) return String
is
   Result : String (1 .. 10);
   Start  : Natural;

   package Stream_Element_IO is new Ada.Text_IO.Modular_IO (Num =>
Ada.Streams.Stream_Element);
begin -- Hex_Image
   Stream_Element_IO.Put (To => Result, Item => Number, Base => 16);
   Start := Ada.Strings.Fixed.Index (Result, "#") + 1;

   return Result (Start .. Result'Last - 1);
end Hex_Image;

and get it right 1st time, compared to the issues you encountered
duplicating (some of) the functionality of Put, seems to me evidence
that this approach is less error prone. I certainly find it simpler
and clearer, too.

Getting this to return a zero-filled String of the correct number of
digits is slightly more complex:

Num_Chars : constant := Ada.Streams.Stream_Element'Size / 4;

Result : String (1 .. Num_Chars + 10);

...

return String'(1 .. Num_Chars - (Result'Last - Start) => '0') & Result
(Start .. Result'Last - 1);