Re: Enum'Image (Was: Improving Ada's image)

["Frank J. Lhota" <NOSPAM.lhota.adarose@verizon.net>]

"Jacob Sparre Andersen" <sparre@nbi.dk> wrote in message
news:pl4qp57wtw.fsf_-_@sparre.crs4.it...
> That would probably be the best way to do it.  It would keep old
> programs working, and it seems like a logical Ada-like way of doing
> things.
>
>    type Colours is (Red, Green, Blue);
>    for Red'Image use "R";
>    for Green'Image use "G";
>    for Blue'Image use "B";

As an alternative, how about the ability to write your own Image function?

If I had the task of inventing Ada over again, I would make cut a lot of the
attribute functions (such as 'Max, 'Image, 'Value, etc.) and replace them
with inherited subprograms that the programmer would be free to override. In
other words, if you declare

    type Colours is (Red, Green, Blue);

then this type would inherit the function

    function Image( X : in Colours ) return String;

and this inherited function would return one of the strings "RED", "GREEN",
or "BLUE". If this is unacceptable, you could override this version of Image
by writing your own version, and declaring it in the same scope as the type
definition:

    type Colours is (Red, Green, Blue);
    function Image( X : in Colours ) return String;

If Image worked this way, instead of being an attribute, it would be
completely customizable. We can return results in any letter case: upper,
lower, mixed, or custom. The result of Image can contain spaces when this
aids readability. Image can be internationalized, e.g. we can have
Image(Red) return "Red" if the locale is U.S., but return "Rouge" if the
locale is France. The possibilities would be endless.