CT BitArray

[Bastiaan Veelo]

On Thursday, 1 November 2018 at 00:01:04 UTC, Stefan Koch wrote:
> On Wednesday, 31 October 2018 at 23:14:08 UTC, Bastiaan Veelo 
> wrote:
>> Currently, BitArray is not usable at compile time, so you 
>> cannot do
>> ```
>> enum e = BitArray([1, 1, 1, 0]);
>> ```
>> This gives
>>> /dlang/dmd/linux/bin64/../../src/phobos/std/bitmanip.d(1190): 
>>> Error: `bts` cannot be interpreted at compile time, because 
>>> it has no available source code
>>
>> IIUC, that is because `bts` comes from core.bitop but no 
>> source code is there. I am guessing these are filled in by 
>> compiler intrinsics or the like, and they are unavailable at 
>> CT, correct?
>>
>> I suppose that alternative implementations of `btc`, `bts`, 
>> `btr`, `bsf` and `bt` could exist that do not use the runtime 
>> that could be used if(__ctfe) in the implementation of 
>> BitArray, that would make the above code work. Is this 
>> feasible? Is there precedent in phobos? Are there 
>> complications?
>>
>> Thanks!
>
> Oh that ... actually I can fix that with a small patch to dmd.
>
> Tell me which version are you using and I'll make it for you.
>
> Cheers,
>
> Stefan

Thank you, Stefan. At the moment we are using latest stable dmd, 
v2.082.1. I expect to switch to ldc or gdc at a later time. I 
don't think we'll be patching the compiler, support in the 
mainline compilers would be much preferable. It is not a blocker 
either, we can wait as long as it takes and meanwhile use module 
level BitArrays like
```
immutable BitArray e;
static this()
{
     e = BitArray([1, 1, 1, 0]);
}
```

It just seemed like a fixable limitation to me, hence my question 
here. Shall we start with a feature request?

Bastiaan.