Private enum members + Descent

[Justin Johansson]

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