Associative arrays give compile error

[Bob Cowdery]

 On 05/10/2010 15:14, Steven Schveighoffer wrote:
> On Tue, 05 Oct 2010 09:00:13 -0400, Bob Cowdery
> <bob at bobcowdery.plus.com> wrote:
>
>>  On 05/10/2010 13:45, Denis Koroskin wrote:
>
>>> "static this" is called a static constructor and can be used for
>>> classes and modules. The code in static constructor is guarantied to
>>> be called before you use that class/module, it usually happens upon
>>> thread initialization.
>>>
>>> The other solution is better though:
>>>
>>> enum A_RX_FILT = [                // just works
>>>      "6K0": tuple(100.0, 6100.0),
>>>      "2K4": tuple(300.0, 2700.0),
>>>      "2K1": tuple(300.0, 2400.0),
>>>      "1K0": tuple(300.0, 1300.0),
>>>      "500": tuple(500.0, 1000.0),
>>>      "250": tuple(600.0, 850.0),
>>>      "100": tuple(700.0, 800.0)
>>> ];
>> I'm not totally understanding that. Why can enum compute that at compile
>> time and the thing which it is, an associative array cannot. Is it to do
>> with where these things live.
>
> I'd be very wary of this solution.  Recently, enum has been shown to
> construct itself on every use.
>
> So what I think is happening is every time you use A_RX_FILT, it's
> building a brand new AA (you can verify this by looking at the
> disassembly).
>
> I'd recommend the static this solution in order to ensure you are not
> accidentally killing performance by just using that AA.
>
> A while back, Don suggested that all literals should be considered
> immutable.  I agree with him, but Walter still doesn't.  If all
> literals are immutable, then they could be truly constructed at
> compile-time.
>
> -Steve
I'm happy with the static this solution so will leave well alone. I
generally keep mutable and immutable data structures apart so I tend to
agree that literals should be immutable although of course I'm not aware
of the pros and cons.

bob