CTFE pow()

[Iain Buclaw via Digitalmars-d]

On 2 January 2015 at 14:19, Iain Buclaw <ibuclaw at gdcproject.org> wrote:
> On 1 January 2015 at 18:40, H. S. Teoh via Digitalmars-d
> <digitalmars-d at puremagic.com> wrote:
>> On Fri, Jan 02, 2015 at 02:56:16AM +1000, Manu via Digitalmars-d wrote:
>>> Does anyone know how to fix this? Can we please do so? It's been a
>>> problem for like 5 years it seems.
>>> It's a bit insane that we can't resolve any non-linear functions at
>>> compile time.
>>
>> I've been waiting for this since like, forever. We even have a D code
>> implementation of pow() already (thanks to Iain), which *should* have
>> been CTFE-able, if it weren't for CTFE limitations that prohibit
>> reinterpreting float values in binary, which is required for certain
>> basic operations like isInfinite, isNaN, etc..
>>
>> So it seems that the blocker right now is CTFE, which, unfortunately, is
>> not a pretty piece of code, and requires quite a bit of care to get it
>> done right.
>>
>
> The fundamental structure is in place in Target. where the paintAsType
> implementation encodes/decodes from a char buffer (and supports up to
> 512 bytes).  You can add support for painting a double as a ushort[4]
> by adding a loop, decodeInteger(e, buffer), decodeInteger(e,
> buffer+2), etc...
>
> The second part (and more crucial) is adding the capability into CTFE.
> Shouldn't be much work, but I've yet to get round to it.
>
> See: https://github.com/D-Programming-Language/dmd/blob/master/src/target.c#L287
>
>

I've started a branch which works on this.  I expect it will take me a
week to finish with unittests.

Iain.