On 24/10/2009 17:10, Denis Koroskin wrote:
On Sat, 24 Oct 2009 19:00:10 +0400, Justin Johansson <n...@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.
I'd prefer D to have support for:
enum Color { Red, Green, Blue }
Color color; // compile time error
Color? color; // OK
I don't understand why would you want to hide certain enum values. In
the colors example above, what's the rational behind hiding the
RED_OR_GREEN value?
personally I'd like to see D enums replaced by Java style enums which
make more sense to me. D enums are even worse than C enums since you can
write:
enum foo = "text";
which to me looks very similar to:
auto cat = new Dog;
