Conversion of psi(x,y) to/from SymPy

[rwst]

integrate(psi(x), x, algorithm='sympy')
...
/home/ralf/sage/local/lib/python2.7/site-packages/sympy-1.0-py2.7.egg/sympy/core/function.pyc in _sage_(self)
    705         import sage.all as sage
    706         fname = self.func.__name__
--> 707         func = getattr(sage, fname)
    708         args = [arg._sage_() for arg in self.args]
    709         return func(*args)

AttributeError: 'module' object has no attribute 'polygamma'

Previous description:

sage: integrate(1/(x^3 *(a+b*x)^(1/3)), x, algorithm='sympy')
...
AttributeError: 'gamma' object has no attribute '_sage_'

Depends on #20204

Component: interfaces

Keywords: sage, integrate, sympy

Author: Ralf Stephan

Branch/Commit: 9c4119a

Reviewer: Marcelo Forets

Issue created by migration from https://trac.sagemath.org/ticket/16801

[rwst]

comment:1

Duplicate of #15057 which however misses gamma.

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comment:2

Not quite. It appears to be the other direction that's missing.

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comment:3

I think this naturally needs a general solution that uses the conversions dictionary given with every special function in Sage.

[rwst]

Description changed:

--- 
+++ 
@@ -1,3 +1,18 @@
+
+```
+integrate(psi(x), x, algorithm='sympy')
+...
+/home/ralf/sage/local/lib/python2.7/site-packages/sympy-1.0-py2.7.egg/sympy/core/function.pyc in _sage_(self)
+    705         import sage.all as sage
+    706         fname = self.func.__name__
+--> 707         func = getattr(sage, fname)
+    708         args = [arg._sage_() for arg in self.args]
+    709         return func(*args)
+
+AttributeError: 'module' object has no attribute 'polygamma'
+```
+
+Previous description:
 
 ```
 sage: integrate(1/(x^3 *(a+b*x)^(1/3)), x, algorithm='sympy')

[rwst]

comment:4

gamma is now converted from Sympy, the original case however takes very long to doctest. Is there a faster case that returns something with gamma in Sympy?

Also, additionally now, polygamma does not convert, as in integrate(psi(x), x, algorithm='sympy').

[rwst]

Upstream: Not yet reported upstream; Will do shortly.