Private enum members + Descent

[Justin Johansson]

Denis Koroskin Wrote:

> On Sat, 24 Oct 2009 19:00:10 +0400, Justin Johansson <no at spam.com> wrote:
> 
> > Yigal Chripun Wrote:
> >
> >> On 24/10/2009 01:16, Justin Johansson wrote:
> >> > Sorry; subject line mod'ed  just so Ary doesn't miss it.
> >> >
> >> >> enum Color { private UNINITIALIZED = -1, RED, GREEN, BLUE }
> >> >
> >> >> (btw. Interestingly, typing this code into Eclipse with the Descent  
> >> plug-in
> >> >> causes a Java out of heap space malfunction.)
> >> >
> >>
> >> enum Color { RED, GREEN, BLUE }
> >>
> >> void foo(Color* c) {
> >>    if (c !is null) handleColor(*c);
> >> }
> >> what's the need for that UNINITIIALIZED member?
> >
> > Okay; that's one work around for a corner case of my cited use-case, but
> > you don't always want to, or perhaps it is not convenient/elegant to,  
> > use a pointer
> > to data that conveniently fits into a machine register.
> >
> > Perhaps I am wrong but I thought uninit was a good metaphor to  
> > demonstrate
> > the various useful purposes that private enum members might have.
> >
> > Here is another example that might make the concept jell.  Again I may  
> > well be wrong.
> >
> > Consider this hypothetical enum definition together with plausible  
> > comments:
> >
> > enum Color {
> >   RED, GREEN, BLUE,  // these 3 members are available for public  
> > consumption
> >   private RED_WITH_BLUE_POKER_DOTS,  // this value is used internally  
> > and is not for public consumption and that's why it is marked private
> >   private RED_OR_GREEN,  // ditto; internal routine to cater for  
> > red-green color-blindness
> > }
> >
> > The above demonstrates a set of entities that are meaningful to some  
> > possible internal
> > function but otherwise not externally meaningful.
> >
> > Another use-case lies in the API programmer's want for "private" ..
> > so, for example, consider that "private" may well be a synonym for
> > "pleasedontusethismemberbecauseitisalikelycandidateforfuturedeprecation"  
> > **
> >
> > ** Using Walter Bright insignificant whitespace/separator notation :-)
> >
> > Thanks Yigal for commenting and perhaps your further comment?
> >
> > Justin
> >
> 
> Another useful use-case I see is enforcing explicit initialization:
> 
> enum Color
> {
>      private Uninitialized = 0,
>      Red,
>      Green,
>      Blue,
> }
> 
> Color color; // error: Color.Uninitialized is not accessible
> 
> It would work similar to private struct ctors.

Absolutely!

In general, I cannot see any reason why protection modifiers should not
allowable for enums members in the same manner as for members of
structs, classes, et. al.