Re: Infinity (to the nearest integer)

On Tue, Oct 26, 2010 at 6:55 AM, Kevin Reid <kpreid-M/[email protected]> wrote:

> E generally chooses to work with only 64-bit floats as the default.
> Even if it did not, it does not follow that it is mandatory that 32-
> bit NaN is distinguished from 64-bit NaN. We already conflate all
> possible values of the I-forget-what-you-call-them extra data bits of
> the NaN.


> However, all current implementations distinguish 32-bit NaN (if they
> have 32-bit floats) from 64-bit NaN, so that would be a change.
>
> Even if we do not conflate all NaNs, it does not seem to me
> particularly terrible to choose float64 NaN as the non-integer object
> floor/0 and round/0 return when there is no integer to return. On the
> other hand, we could devise an 'integer NaN' object, which would have
> the advantage of being designed to correspond to the integer protocol
> rather than the float protocol.


I haven't tracked this topic in detail, so I may be misinterpreting Kevin's
statement above, but here is my concern:

If an implementation chooses to distinguish 32-bit and 64-bit floating point
types, it absolutely must not return the same object for NaN in the two
cases. While E is dynamically typed, it is a terrible idea to introduce
behavior that reduces our ability to statically type check portions of the
language.

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