Re: [Chicken-users] EQV? and NaN

[Aleksej Saushev]

  Hello!

John Cowan <address@hidden> writes:

> I'd like to propose a minor change to the semantics of EQV?.  For good
> reasons, = returns #f if either argument is NaN, and currently EQV?
> defers to = if both its arguments are numeric.  However, conceptually
> EQV? is about "sameness" rather than "equality", and all NaNs are
> conceptually "the same".

Sorry? This is plain wrong.

Two different NaNs are _not_ the same, and there exist at least two
different NaNs (signalling and quiet, see IEEE 754). Two different
signalling NaNs are _not_ the same, since they encode _different_ events.
At least the _may_ be different.

> Therefore, I think Chicken should be changed so that (eqv? +nan.0
> +nan.0) => #t.  All existing Schemes that support NaN at all already do
> this, with the exception of SISC, which bizarrely returns #t if *either*
> argument is NaN.

Given that "-nan.0" returns "+nan.0" this should be quiet NaN, right?
There may exist two different ways to get "+nan.0" and these may be different
per standard.


-- 
HE CE3OH...