floats default to NaN... why?

[Andrew Wiley]

On Sat, Jun 9, 2012 at 4:53 PM, Andrew Wiley <wiley.andrew.j at gmail.com> wrote:
>
> On Sat, Jun 9, 2012 at 11:57 AM, Kevin <kevincox.ca at gmail.com> wrote:
>>
>> On Sat 09 Jun 2012 14:59:21 EDT, Jerome BENOIT wrote:
>> >
>> >
>> > On 09/06/12 20:48, Kevin wrote:
>> >> On 09/06/12 14:42, Minas wrote:
>> >>>> With
>> >>>> ints, the best we can do is 0. With floats, NaN makes it better.
>> >>>
>> >>> With the logic that NaN is the default for floats, 0 is a very bad
>> >>> choice for ints. It the worst we could do. Altough I understand that
>> >>> setting it to something else like -infinity is still not a good
>> >>> choice.
>> >> Is it just me but do ints not have infinity values?
>> >
>> > in Mathematics yes, but not in D.
>> >
>> >  I think ints should
>> >> default to about half of their capacity (probably negative for
>> >> signed).
>> >
>> > This would be machine depends, as such it should be avoided.
>> >
>> >> This way you are unlikely to get an off-by-one for an uninitialized
>> >> values.
>> >
>> > something as a Not an Integer NaI should be better.
>>
>> I just don't think it is a good idea to add more metadata to ints.
>>
>
> I agree. With floats, NaN is implemented in hardware. The compiler doesn't
> have to check for NaN when emitting assembly, it just emits operations
> normally and the hardware handles NaN like you'd expect.
> If we tried to add a NaN-like value for integers, we would have to check
> for it before performing integer math. Even with value range propagation, I
> think that would injure integer math performance significantly.

Crap, my apologies for responding with HTML.