Getting a one-touch option (was: Ada95 tutorials with sample code)

[Mario Amado Alves <maa@di.fct.unl.pt>]

> procedure Xyz is
> 
>   opt_is : character := ' ';
> 
> begin
> 
>   while opt_is /= 'V' and then opt_is /= 'A' loop
>     Put( opt_prompt );
>     NEW_LINE;
>     Ada.Text_IO.Put_Line( "Please enter either a 'V' or an 'A' );
>     Get( opt_is );
>     opt_is := To_Upper(opt_is);
>   end loop;
> 
> end Xyz;

Lately I have been using enumerations and exceptions for this kind of
problem:

  type Options is (A, V);
  Option: Options;
  C: Character;
begin
  loop
    Put("Please enter either a 'V' or an 'A'");
    Get_Immediate(C);
    begin
      Option := Options'Value(C & "");
      exit;
    exception
      when Constraint_Error => null;
    end;
  end loop;

There is of course more to be said about "exception-oriented" programming. 
Let us save that for the Ada-Europe'2001 workshop ;-)

| |,| | | |RuaFranciscoTaborda24RcD 2815-249CharnecaCaparica 351+939354005
|M|A|R|I|O|
|A|M|A|D|O|DepartmentoDeInformaticaFCT/UNL 2825-114 Caparica 351+212958536
|A|L|V|E|S|                                                  fax 212948541
| | | | | |                 maa@di.fct.unl.pt                FCT 212948300