Re: Newbie question on Ada TExt_IO

[Preben Randhol <randhol+news@pvv.org>]

On 3 Oct 2002 11:20:24 -0700, Justin wrote:
> How can I handle this?  From my take on what I've read I should avoid
> exception handling for things I'm not expecting, so I've ruled out
> exceptions, that leaves me with obtaining a value of generic type and
> evalutating the type at run-time...how can I do this?  Is this the
> right strategy?

No I would have used exceptions here. I find it difficult to see how you
can avoid it.

I recommend that you look at http://www.it.bton.ac.uk/staff/je/adacraft/ because
it has a lot of nice examples to start with.

Here is my implementation:

---------------------------------------------------------------
with Ada.Text_IO; use Ada.Text_IO;

procedure Feedback
is
   Input    : String(1..80);
   Last     : Integer;
begin

   --  This example will loop until you give a correct number

   loop
      Put ("Please enter a number between 1 and 6 : ");
      Get_Line (Item => Input, Last => Last);

      --  I now choose a block because then I can
      --  put a exception handler inside so that you will
      --  be asked for a number until you give a correct
      --  number

      declare
         --  Making a type that is from 1 to 6. If the character
         --  you convert isn't in the range 1..6 then Constraint_Error 
         --  will be raised and we can handle it.

         type Input_Number_Type is range 1..6;
         Number : Input_Number_Type;
      begin
         --  we convert Input (1..1) to our Input_Number_Type

         Number := Input_Number_Type'Value (Input (1..1));

         Put_Line ("Thank you!");
         --  OK conversion went well. (If it hadn't the program would
         --  jump to exception below before instead of continuing)

         exit;
         --  Jumping out of the loop.

      exception
         when Constraint_Error =>
         Put_Line ("Wrong number!");
      end;
   end loop;

end Feedback;

Preben
-- 
Ada95 is good for you.
http://libre.act-europe.fr/Software_Matters/02-C_pitfalls.pdf