Re: Type detection

["Björn Persson" <spam-away@nowhere.nil>]

Robert I. Eachus wrote:

> Björn Persson wrote:
> 
>> For the special case of distinguishing integer types from enumeration 
>> types, I've been thinking of using something like this...
> 
> I extended the idea a little further, [...]

With these additions:

>   type Unsigned_16 is mod 2**16;
   subtype Usub is Unsigned_16 range 3 .. 12;
   subtype Csub is Character range 'b' .. 'c';
>   type Weekday is (Monday, Tuesday, Wednesday, Thursday, Friday);
> 
>   function Find_Boolean is new Find_Datatype(Boolean);
>   function Find_Integer is new Find_Datatype(Integer);
>   function Find_Character is new Find_Datatype(Character);
   function Find_Csub is new Find_Datatype(Csub);
>   function Find_Unsigned is new Find_Datatype(Unsigned_16);
   function Find_Usub is new Find_Datatype(Usub);
>   function Find_Enumeration is new Find_Datatype(Weekday);
> 
> begin
> 
>   Ada.Text_IO.Put_Line(" Find_Boolean returned " & Find_Boolean);
>   Ada.Text_IO.Put_Line(" Find_Integer returned " & Find_Integer);
>   Ada.Text_IO.Put_Line(" Find_Character returned " & Find_Character);
   Ada.Text_IO.Put_Line(" Find_Csub returned " & Find_Csub);
>   Ada.Text_IO.Put_Line(" Find_Unsigned returned " & Find_Unsigned);
   Ada.Text_IO.Put_Line(" Find_Usub returned " & Find_Usub);
>   Ada.Text_IO.Put_Line(" Find_Enumeration returned " & Find_Enumeration);

I get this output:

  Find_Boolean returned Enumeration
  Find_Integer returned Integer
  Find_Character returned Enumeration
  Find_Csub returned Enumeration?
  Find_Unsigned returned Unsigned
  Find_Usub returned Enumeration?
  Find_Enumeration returned Enumeration

I think using 'Base here too would be better:

 >         if Unknown'Succ(Unknown'Last) = Unknown'First
         if Unknown'Succ(Unknown'Base'Last) = Unknown'Base'First

Then I get:

  Find_Boolean returned Enumeration
  Find_Integer returned Integer
  Find_Character returned Enumeration
  Find_Csub returned Enumeration too
  Find_Unsigned returned Unsigned
  Find_Usub returned Unsigned
  Find_Enumeration returned Enumeration

-- 
Björn Persson

jor ers @sv ge.
b n_p son eri nu