[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: Using the GNU GMP Library for Bignums in Emacs

From: Achim Gratz
Subject: Re: Using the GNU GMP Library for Bignums in Emacs
Date: Sun, 22 Jul 2018 21:57:27 +0200
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux)

Ken Raeburn writes:
> If we’re going to treat NaNs as having distinguishable bit patterns so
> we can tell whether two are the same or not, should we also have
> printable/readable forms that distinguish them? If not, how do we
> create and use distinguishable NaNs?

That would expose the NaN payload, using the non-specified bits of the
mantissa of an NaN to transport (sideband) information.  You will
probably find that no one really expects these bits to be used…

> For that matter, are we guaranteed that operations like (/ 0.0 0.0)
> will always generate NaNs with the same bit pattern?

On the same platform? Likely.  On different platforms, surely not.

> I would’ve guessed that it might be preferable to go the other
> direction, and use one canonical NaN value in Lisp, which would thus
> always be eq/eql to all other NaN expressions.

Ignoring the payload bits would probably be OK, but that still gives you
at least two different NaN (positive and negative) to deal with.

+<[Q+ Matrix-12 WAVE#46+305 Neuron microQkb Andromeda XTk Blofeld]>+

SD adaptation for Waldorf Blofeld V1.15B11:

reply via email to

[Prev in Thread] Current Thread [Next in Thread]