#9240: applying full_simplify() to gamma functions causes an error
---------------------------------------------------------------+------------
Reporter: tomc |
Owner: tomc
Type: defect |
Status: needs_review
Priority: major |
Milestone: sage-4.7.1
Component: symbolics |
Keywords: gamma function, full_simplify, factorial
Work_issues: |
Upstream: N/A
Reviewer: Dan Drake, Karl-Dieter Crisman, François Bissey |
Author: Tom Coates, Burcin Erocal
Merged: |
Dependencies: #11415
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Changes (by kcrisman):
* reviewer: Dan Drake, Karl-Dieter Crisman => Dan Drake, Karl-Dieter
Crisman, François Bissey
Comment:
Thanks, I think that helps a ''little''. I also found
{{{
cdef _register_function(self):
# We don't need to add anything to GiNaC's function registry
# However, if any custom methods were provided in the python
class,
# we should set the properties of the function_options object
# corresponding to this function
cdef GFunctionOpt opt =
g_registered_functions().index(self._serial)
if hasattr(self, '_eval_'):
opt.eval_func(self)
}}}
which I knew about before.
I am going to have to write down '''exactly''' how all this works at Sage
Days 31, because I do not want to be rediscovering this from scratch every
time like I am now.
----
I have some more questions, presumably for Burcin. I don't think they
are big deals, but I don't feel comfortable giving positive review without
knowing them. Someone else who knows more might!
* why the change from the 'billions of digits' error message to the
symbolic answer? This seems like a big change - someone might rely on
that type of entry failing in number theory. Note that the multifactorial
still has the 'billions of digits' error message, incidentally.
* what would the problem be if Ginac got symbolic answers back, if it
didn't have anything for those before? (Not criticizing, just not
understanding. I don't have a problem with them being numeric for ints
and floats and longs.)
* Why did you remove `opt.set_python_func() `? I assume this has
something to do with fbissey's comment.
* Does ` return None ` just mean that Ginac will not try to
evaluate things like `factorial(sqrt(2))` internally?
----
Status:
* Positive review on Tom's patch, from Dan Drake.
* The log gamma stuff is fine.
* Apparently Francois is happy with the && to & switch. This is beyond
me, though I don't see any problems with it.
* The actual changes to and new factorial and gamma functions are fine.
* Need answer to questions, or someone else to review those pieces in
lieu of that.
* Finally, the big question - WHY this change? I can't find a single
doctest that tells me what broke with Tom's patch but without Burcin's
patch. I feel there must be some very subtle Maxima output that could
have come out incorrect, but I cannot find it. All these doctests should
have worked before (or were cdef functions so they couldn't be doctested).
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/9240#comment:12>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
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