[Maxima-discuss] numeric/bigfloat class WAS #4636 signum(ind) is an error

[Stavros M. <mac...@gm...>]

Agreed that discussion of numeric.lisp/bigfloat should be a new thread. So
here it is.

You say:

So in your example of (bigfloat::expt (bigfloat:to 4) (bigfloat:to '((rat)
1 2))), the args are a CL fixnum and a CL ratio. By the rules of CL, the
result is a single-precision result.

OK, but those aren't the rules of Maxima...!

(I don't remember exactly where the to name came from, but there was a
Maxima function to that did something similar.)

I'd think "to" means "convert-to", no?

You've probably forgotten that 1e0 and 1f0 are the same precision.

The Maxima reader treats them as the same, but in this case,
single-precision was the *return value*, and they're not the same Lisp type
and don't print the same in Maxima:

(type-of 1.0f0) => SINGLE-FLOAT
(/ 1.0f0 3) => 0.33333334f0
($print 1.0f0) => 1.0f0


(type-of 1.0e0) => DOUBLE-FLOAT

(/ 1.0e0 3) => 0.3333333333333333

($print 1.0e0) => 1.0



On Sun, Nov 30, 2025 at 11:15 PM Raymond Toy via Maxima-bugs <
max...@li...> wrote:

> This should probably be a new issue or a discussion on the mailing list.
> Like the rest of Maxima, I didn't write any design docs. :-( The only
> documentation is the code and comments in src/numeric.lisp. However the
> general idea with the functions in the bigfloat package is to mimic what CL
> does, except when one (or more) operands are bfloats, in which case the
> result is a bfloat. Also bigfloat:to returns a numeric type. If the arg
> is a CL type, that's what you get. If it's a bfloat, you get a bigfloat
> object.
>
> By doing it this way, you could write one function that would handle CL
> numeric types or bfloats without changing the function. Of course, if speed
> mattered, you'd write a special double-float version. But the bfloat
> version could very possibly be identical, if some care is taken to compute
> an epsilon value appropriately.
>
> So in your example of (bigfloat::expt (bigfloat:to 4) (bigfloat:to
> '((rat) 1 2))), the args are a CL fixnum and a CL ratio. By the rules of
> CL, the result is a single-precision result.
>
> (I don't remember exactly where the to name came from, but there was a
> Maxima function to that did something similar.)
>
> You've probably forgotten that 1e0 and 1f0 are the same precision.
>
> I should probably convert some of the comments in to docstrings so you can
> easily look up what they do via cl:describe.
> ------------------------------
>
> *[bugs:#4636] <https://sourceforge.net/p/maxima/bugs/4636/> signum(ind) is
> an error*
>
> *Status:* open
> *Group:* None
> *Labels:* extended real signum limit
> *Created:* Thu Nov 27, 2025 12:41 PM UTC by Barton Willis
> *Last Updated:* Sun Nov 30, 2025 02:27 PM UTC
> *Owner:* nobody
>
> Either a signum nounform or ind is a better result than an error:
>
> (%i4)   signum(ind);
> sign: sign of ind is undefined.
>
> Should the general simplifier, or the one‑argument limit function, handle
> F(extended-real)? We’ve discussed this—do we have a consensus?
> ------------------------------
>
> Sent from sourceforge.net because max...@li... is
> subscribed to https://sourceforge.net/p/maxima/bugs/
>
> To unsubscribe from further messages, a project admin can change settings
> at https://sourceforge.net/p/maxima/admin/bugs/options. Or, if this is a
> mailing list, you can unsubscribe from the mailing list.
> _______________________________________________
> Maxima-bugs mailing list
> Max...@li...
> https://lists.sourceforge.net/lists/listinfo/maxima-bugs
>