Type detection

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

Axel Druesnes wrote:

>  i am currently writing a generic package. Despite being really generic 
> one (at least) particular type need a special handling in two functions. 
> I am therefore wondering how i can either detect the type... 

[...]

> function Type_Id ( Value : in Boolean ) return E_Type_Id;
> function Type_Id ( Value : in Integer ) return E_Type_Id;
> 
> -- Inside the body
> procedure I_Need_The_Type ( Value : Generic_Type )
> ....
> Type_Identifier := Type_Id ( Value ); -- i wish it worked here

For the special case of distinguishing integer types from enumeration 
types, I've been thinking of using something like this:

    if Ada.Characters.Handling.Is_Letter
         (Generic_Type'Image(Generic_Type'First)(1)) then
       -- It's an enumeration.
    else
       -- It's an integer type.
    end if;

Further tests could be done to see if an enumeration is Boolean or 
something else.

For more general cases, since the type is known when you instantiate the 
generic package, maybe you can pass an extra parameter (of type 
E_Type_Id)? Or you could keep the common parts in one highly generic 
package and then have a number of more specific generic packages for 
different types. The more specific packages would then instantiate the 
highly generic package and call the common subprograms in it.

-- 
Björn Persson

jor ers @sv ge.
b n_p son eri nu