Re: [PATCH] Re: Bignum performance

[Simon Leinen]

Emacs also has `most-negative-fixnum' and `most-positive-fixnum' (borrowed from Common Lisp but now part of the core).

On my 64-bit system (GNU Emacs 30.0.50 on aarch64-apple-darwin22.5.0):

(= (- (expt 2 61)) most-negative-fixnum) ⇒ t
(= (1- (expt 2 61)) most-positive-fixnum) ⇒ t

(Same as on Emanuel's.)

-- 

Simon.

On Wed, Aug 16, 2023 at 1:12 PM Emanuel Berg <incal@dataswamp.org> wrote:

Gerd Möllmann wrote:

>> I don't know about SBCL, but as for Emacs, refer to the
>> definition of VALBITS in lisp.h (maybe also the right files
>> among m/*.h and s/*.h, but I have no idea where they've
>> disappeared to.)
>
> The SBCL I have here, a Homebrew installation, uses the
> scheme where
>
> ....0 -> fixnum
> ....1   -> other objects (discriminated by additional tag bits)
>
> I had the same for Emacs in the branch gerd_int in the
> 2000s, if memory serves me.

Ah, there is `fixnump' (and `bignump') to test for a specific
number,

  (fixnump (expt 2 60)) ; t
  (fixnump (expt 2 61)) ; nil

2^60 = 1152921504606846976, so that's pretty big.

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