provide wrapper for psi function of GiNaC

[burcin]

From sage-support:

On Fri, 18 Sep 2009 15:47:45 -0700 (PDT)
The_Fool <masterfulet@yahoo.com> wrote:

> While working with the derivative of the Gamma function, the digamma
> function is obviously involved.  The sage "diff" function does show Γ
> '(x) == Γ(x)ψ(x) like it should, however, the digamma function (called
> psi in sage) is not defined whenever I try to do anything with it.  It
> seems as if only the output of "diff" can use this function.

psi() is defined in GiNaC, but we don't provide wrappers for it.

Defining a function psi, similar to the way arctan2 is defined in line 422 of sage/functions/trig.py should fix this.

The sage-support thread is here:

http://groups.google.com/group/sage-support/browse_thread/thread/1ad313c921b7dbc0

Component: symbolics

Keywords: psi, gamma, digamma, polygamma

Author: Burcin Erocal

Reviewer: Karl-Dieter Crisman, Ross Kyprianou, Minh Van Nguyen

Merged: sage-4.3.3.alpha1

Issue created by migration from https://trac.sagemath.org/ticket/6961

[zimmermann6]

comment:1

More precisely:

sage: diff(gamma(x), x)
gamma(x)*psi(x)

but "psi" is unknown to Sage...

[burcin]

Attachment: trac_6961-psi.patch.gz

wrappers for psi function from pynac

[burcin]

Author: Burcin Erocal

[burcin]

comment:2

It turns out defining this function wasn't as straightforward as I thought. Pynac defines 2 functions with the same name psi. :)

attachment: trac_6961-psi.patch wraps these 2 functions, and provides a global psi() to call the appropriate one. Unpickling these correctly requires changes in pynac. I'll make a new pynac package available later this week.

[burcin]

comment:3

New pynac package available here:

http://sage.math.washington.edu/home/burcin/pynac/pynac-0.1.11.spkg

The package contains fixes for #7822, #6961, #7876, #7363, #6465 and #6559. From these #7876 and #7363 contain printing fixes. Doctests should be run at least with patches from these two tickets.

[sagetrac-mvngu]

comment:4

The patch on this ticket conflicts with #6207. If I first apply the patches on #6207 to Sage 4.3.1, and then trac_6961-psi.patch, I would get a hunk failure:

[mvngu@sage sage-main]$ hg qimport https://github.com/sagemath/sage-prod/files/10645085/trac_6207.patch.gz && hg qpush
adding trac_6207.patch to series file
applying trac_6207.patch
now at: trac_6207.patch
[mvngu@sage sage-main]$ hg qimport https://github.com/sagemath/sage-prod/files/10645086/trac_6207-part2.patch.gz && hg qpush
adding trac_6207-part2.patch to series file
applying trac_6207-part2.patch
now at: trac_6207-part2.patch
[mvngu@sage sage-main]$ hg qimport https://github.com/sagemath/sage-prod/files/10645087/trac_6207-review.patch.gz && hg qpush
adding trac_6207-review.patch to series file
applying trac_6207-review.patch
now at: trac_6207-review.patch
[mvngu@sage sage-main]$ hg qimport https://github.com/sagemath/sage-prod/files/10646152/trac_6961-psi.patch.gz && hg qpush
adding trac_6961-psi.patch to series file
applying trac_6961-psi.patch
patching file sage/symbolic/pynac.pyx
Hunk #2 FAILED at 1566
1 out of 3 hunks FAILED -- saving rejects to file sage/symbolic/pynac.pyx.rej
patch failed, unable to continue (try -v)
patch failed, rejects left in working dir
errors during apply, please fix and refresh trac_6961-psi.patch

Perhaps you want to rebase trac_6961-psi.patch on top of #6207?

[sagetrac-mvngu]

Work Issues: needs rebase on top of #6207