Re: Extended 'Succ attribute?

["Adam Beneschan" <adam@irvine.com>]

Jérémie Lumbroso wrote:
> Hello,
>
> I just started Ada and was wondering if there is a way to make the Succ
> attribute of discrete types behave in a cyclic manner (akin to the
> modular type):
>
>     type T_DAY is (Mon, Tue, Wed, Thu, Fri, Sat, Sun);
>
>     ...
>
>     day := T_DAY'(Sun);
>     day := T_DAY'Succ(day);  -- that this returns 'Mon' instead of
>                              -- a type constraint error
>
> I could of course define my own function to do this, but I wish to know
> if there is a way to get Ada to do it itself.

No.

The best you could do would be to declare a modular type, and then
declare Mon, Tue, etc. as constants of that type:

    type T_DAY is mod 7;
    Mon : constant T_DAY := 0;
    Tue : constant T_DAY := 1;
etc.

Then T_DAY'Succ(X) will wrap around.  But I don't see any advantage to
doing things this way.  I'd
just make it an enumeration literal and define your own Succ function.

                        -- Adam