On Apr 14, 2016, at 9:49 PM, Stephen Canon <[email protected]> wrote:
>> On Apr 14, 2016, at 4:55 PM, Stephen Canon via swift-evolution 
>> <[email protected] <mailto:[email protected]>> wrote:
>>> Provide basic constants (analogues of C's DBL_MAX, etc.)
>> Nice, have you considered adding pi/e and other common constants?  I’d 
>> really really like to see use of M_PI go away… :-)
> 
> That’s a reasonable suggestion.  I’m not sure if FloatingPoint is the right 
> protocol to attach them to, but I’m not sure that it’s wrong either.  I’d be 
> interested to hear arguments from the community either way.

I’m not sure where the right place is either, I just want them :-)   Seriously 
though, the notion of pi seems to make sense for both decimal and binary fp 
types, it seems base independent.

>> Swift supports instance and type members with the same names, but this is 
>> controversial, leads to confusion, and may go away in the future.  It would 
>> be great to avoid this in your design.
> 
> Interesting.  Both are definitely useful, but Type(1).ulp is sufficiently 
> simple that only having the instance member may be good enough.  Otherwise, 
> ulpOfOne or similar could work.

Either of those work for me.

> 
>> I’m certainly not a floating point guru, but I would have expected 
>> significant to be of type RawSignificand, and thought that the significant 
>> of a nan would return its payload.  Does this approach make sense?
>> 
>> … later: I see that you have this on the binary FP type, so I assume there 
>> is a good reason for this :-)
> 
> Both are useful to have in practice.  I have been attempting to keep the 
> assumptions about representation to a minimum in the top-level FloatingPoint 
> protocol.

Makes sense!

>> I’m used to this being called a “Denormal”, but I suspect that “subnormal” 
>> is the actually right name?  Maybe it would be useful to mention the 
>> “frequently known as denormal” in the comment, like you did with mantissa 
>> earlier.
> 
> Yes, “subnormal” is the preferred IEEE 754 terminology, but I’ll add a note 
> referencing “denormal” as well.

Thanks!

-Chris

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