2 problems I can't get my head around

[Manu]

On 26 November 2012 15:27, monarch_dodra <monarchdodra at gmail.com> wrote:

> On Monday, 26 November 2012 at 13:08:57 UTC, Manu wrote:
>
>> On 26 November 2012 15:00, monarch_dodra <monarchdodra at gmail.com> wrote:
>>
>>  On Monday, 26 November 2012 at 12:46:10 UTC, Manu wrote:
>>>
>>>  On 26 November 2012 14:39, Andrej Mitrovic <andrej.mitrovich at gmail.com
>>>> >**
>>>>
>>>> wrote:
>>>>
>>>>  On 11/26/12, Manu <turkeyman at gmail.com> wrote:
>>>>
>>>>> > 1.
>>>>> >
>>>>> > enum i = 10;
>>>>> > pragma(msg, is(i == enum) || is(typeof(i) == enum)); // <-
>>>>> > > false?!
>>>>> >
>>>>> > I can't find a way to identify that i is an enum, not a > > variable;
>>>>> can not
>>>>> > be assigned, has no address, etc.
>>>>>
>>>>> It's not an enum, it's a manifest constant.
>>>>>
>>>>>
>>>>>  Well that's certainly not intuitive. I've never even heard that term
>>>> before. It looks awfully like an enum, with the whole 'enum' keyword and
>>>> all ;)
>>>> How do I detect that then?
>>>>
>>>>
>>> The term enum (AFAIK) is comes from an old C++ hack, where you'd create
>>> an
>>> actual enum to represent variable that's useable compile-time.
>>>
>>> Anyways, when you declare an actual enumerate, you have to declare:
>>> 1) The enum type
>>> 2) The enum values
>>> 3) The enum variable
>>>
>>> So in your case, it would have to be:
>>> --------
>>> enum Enumerate
>>> {
>>>    state1 = 10,
>>>    state2
>>> }
>>> Enumerate i = Enumerate.state1;
>>> -----
>>>
>>>
>> I'm not looking for a hot-to use enums, I need to know how to form an
>> expression to make the pragma show true in precisely that context.
>>
>
> Is see, but (unfortunatly), as already mentioned, the keyword "enum" is
> also used to create a manifest constant. That means the tests you are
> giving your i are irrelevant.
>
> If you really want to test a manifest constant, then I guess you can test
> for the "lvalue-ness" of your variable:
>     enum i = 10;
>     int j = 10;
>     pragma(msg, __traits(compiles, (ref typeof(i) x) { } (i)));
>     pragma(msg, __traits(compiles, (ref typeof(j) x) { } (j)));
>
> of the "Compile time knowability"
>     enum i = 10;
>     int j = 10;
>     pragma(msg, __traits(compiles, () {int[i] a;}));
>     pragma(msg, __traits(compiles, () {int[j] a;}));
>
> That said, it is not an "iff" relation. I do not know of any way to test
> if something is *only* a manifest constant...
>

That's sooo brutal! But it works, I'll use the first one, the second
depends on i being an int.
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