#11888: Sage is missing the lambert_w function
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Reporter: benjaminfjones
| Owner: burcin
Type: defect
| Status: needs_work
Priority: minor
| Milestone: sage-5.0
Component: symbolics
| Keywords: lambert_w symbolics conversion maxima sd35.5
Work_issues:
| Upstream: N/A
Reviewer: Keshav Kini, Karl-Dieter Crisman, Fredrik Johansson, Burcin
Erocal | Author: Benjamin Jones
Merged:
| Dependencies: #12507
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Comment(by burcin):
Replying to [comment:31 benjaminfjones]:
> I've written a new patch that includes significant changes compared to
the last one. I think I've included all of burcin's suggestions and I
think it's much improved now. All tests pass with the patch applied on
5.0.beta4 + #12507.
Thanks! The patch looks really good. When checking if the input is 0 in
`_eval_`, you might want to `return z` instead of `Integer(0)` to preserve
the type of the input. Similarly, we should return `parent(z)(1)` or
`parent(z)(-1)` in the other branches.
<snip>
> I guess that's because there isn't a two-argument version of lambert_w
defined in maxima. The conversion maxima -> Sage works (as shown in one of
the doctests) but it looks like the other way doesn't. Another example:
>
> {{{
> sage: maxima(lambert_w(5))
> Maxima ERROR:
>
> lambert_w: wrong number of arguments.
> -- an error. To debug this try: debugmode(true);
> }}}
>
> Q: How do I get around this?
You need to define `_maxima_init_evaled_()`. See line 895 of
`sage/fuctions/other.py`:
http://hg.sagemath.org/sage-
main/file/c239be1054e0/sage/functions/other.py#l895
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Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/11888#comment:33>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
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