Re: output and digits

[Robert A Duff <bobduff@shell01.TheWorld.com>]

"Staszek Goldstein" <goldstei@math.uni.lodz.pl> writes:

> >    type Roman_Digit is ('I','V','X','L','C','D','M');
> >    for Roman_Digit use ('I' => Character'('I')'val,
> >                         'V' => ...);
> >
> > Then Unchecked_Conversion from Roman_Digit to Character will work.
> > Except that you then need to order the Roman_Digits in the same
> > order as in Character: "... is ('C', 'D', ..., 'X')".
> 
> This works (if you correct it slightly to integer(character'pos('I')) - pos
> gives a universal integer!), but changing the order does not seem nice in a
> language like Ada...

Oops.  Yeah, 'Pos is what you want.  But you don't need the conversion
to Integer.

What you *really* want is:

    subtype Roman_Digit is Character
        restricted to ('I','V','X','L','C','D','M'); -- Not Ada!

or perhaps:

    type Roman_Digit is new Character
        restricted to ('I','V','X','L','C','D','M'); -- Not Ada!

Actually, it makes no sense to do arithmetic on roman numerals.
So if I were doing this, I would have two functions, for converting
integers to/from roman numerals represented as Strings.
You only need roman numerals for I/O.  All internal processing
can be done in integers.

That's how you'd do it an any language.

- Bob