Question/request/bug(?) re. floating-point in dmd

[John Colvin]

On Wednesday, 6 November 2013 at 06:28:59 UTC, Walter Bright 
wrote:
> On 11/5/2013 8:19 AM, Don wrote:
>> On Wednesday, 30 October 2013 at 18:28:14 UTC, Walter Bright 
>> wrote:
>>> Not exactly what I meant - I mean the algorithm should be 
>>> designed so that
>>> extra precision does not break it.
>>
>> Unfortunately, that's considerably more difficult than writing 
>> an algorithm for
>> a known precision.
>> And it is impossible in any case where you need full machine 
>> precision (which
>> applies to practically all library code, and most of my work).
>
> I have a hard time buying this. For example, when I wrote 
> matrix inversion code, more precision was always gave more 
> accurate results.

I had a chat with a fluid simulation expert (mostly plasma and 
microfluids) with a broad computing background and the only 
algorithms he could think of that are by necessity fussy about 
max precision are elliptical curve algorithms.

>
>> A compiler intrinsic, which generates no code (simply 
>> inserting a barrier for
>> the optimiser) sounds like the correct approach.
>>
>> Coming up for a name for this operation is difficult.
>
> float toFloatPrecision(real arg) ?