Opened 8 years ago
Closed 7 years ago
#18085 closed defect (fixed)
missing binding for SymPy's exp_polar()
Reported by:  kalvotom  Owned by:  

Priority:  minor  Milestone:  sage7.1 
Component:  symbolics  Keywords:  sd66 
Cc:  vdelecroix, sstarosta, kcrisman  Merged in:  
Authors:  Tomáš Kalvoda  Reviewers:  Ralf Stephan 
Report Upstream:  N/A  Work issues:  
Branch:  6d3aeaa (Commits, GitHub, GitLab)  Commit:  6d3aeaa73c6052f691a2d3cd06cd1049cc6843ff 
Dependencies:  #20185  Stopgaps: 
Description (last modified by )
The following integral cannot be evaluated by maxima:
sage: integrate(1/sqrt(1+x^3),x) integrate(1/sqrt(x^3 + 1), x)
With 'sympy' algorithm the computation fails:
sage: integrate(1/sqrt(1+x^3),x,algorithm='sympy') ... AttributeError: 'gamma' object has no attribute '_sage_'
However, SymPy? can compute the integral and gives the result in terms of gamma and hypergeometric functions:
sage: import sympy sage: sympy.integrate(1/sqrt(1+x**3)) x*gamma(1/3)*hyper((1/3, 1/2), (4/3,), x**3*exp_polar(I*pi))/(3*gamma(4/3))
It can be seen that not only gamma
is a problem (already fixed in sympy master) but also exp_polar
which Sage does not know.
This ticket should track the status of the Sympy pull request fixing the exp_polar
issue, and it should implement a skeleton exp_polar
on the Sage side.
Change History (19)
comment:1 Changed 8 years ago by
comment:2 Changed 8 years ago by
After some more digging it turned out the this is almost OK in the most recent git version of Sympy (not 0.7.6 which is shipped with Sage). Class Function has a _sage_ method and hypergeometric function hyper
is also correctly dealt with.
However, the example mentioned above still fails because Sage does not know exp_polar
function. I have created this pull request which adds _sage_
method to exp_polar
and returns the usual exponential.
Tomáš
comment:3 Changed 8 years ago by
Report Upstream:  N/A → Reported upstream. No feedback yet. 

comment:4 Changed 8 years ago by
I have commented on the pull request, https://github.com/sympy/sympy/pull/9224
comment:5 Changed 8 years ago by
Cc:  kcrisman added 

Description:  modified (diff) 
Summary:  Symbolic integration and SymPy → missing binding for SymPy's exp_polar() 
comment:6 Changed 8 years ago by
If you want to do try your hands at it, see http://trac.sagemath.org/wiki/symbolics/functions for symbolic function tickets, and https://github.com/sagemath/sage/compare/develop...rwst:special for a collection of most recent code examples.
comment:7 Changed 8 years ago by
Branch:  → u/kalvotom/missing_binding_for_sympy_s_exp_polar__ 

comment:8 Changed 8 years ago by
Authors:  → Tomáš Kalvoda 

Commit:  → 0683dd3c7f980d4a2f274a200bdcd4f69073c730 
Report Upstream:  Reported upstream. No feedback yet. → Fixed upstream, in a later stable release. 
New commits:
0683dd3  add exp_polar function

comment:9 followup: 10 Changed 8 years ago by
I have doctested the function with git version of Sympy and all tests passed (especially the one with integration). I guess we have to wait for a new version of Sympy to arrive in Sage (probably Sympy 0.7.7).
Anyway, this is my first attempt to contribute to Sage, so feel free to knitpick.
I have one question. How complicated it would be to force Sage to perform simplifications like
sage: exp_polar(2 + 5*I)*exp_polar(5  I) exp_polar(7 + 4*I)
My current understanding is that such simplifications are taken care of by an external library ( Pynac ) and there is no way how to do this in Sage alone, am I right?
comment:10 Changed 8 years ago by
Replying to kalvotom:
I have doctested the function with git version of Sympy and all tests passed (especially the one with integration). I guess we have to wait for a new version of Sympy to arrive in Sage (probably Sympy 0.7.7).
Yes, other tickets are waiting for that too.
Anyway, this is my first attempt to contribute to Sage, so feel free to knitpick.
Will get to it.
I have one question. How complicated it would be to force Sage to perform simplifications like
sage: exp_polar(2 + 5*I)*exp_polar(5  I) exp_polar(7 + 4*I)My current understanding is that such simplifications are taken care of by an external library ( Pynac ) and there is no way how to do this in Sage alone, am I right?
I think so, but I'm not much into Pynac. Anyway, it could be part of Python Sage by including a function that does it in one of the Expression.simplify*
methods.
comment:11 Changed 8 years ago by
Branch:  u/kalvotom/missing_binding_for_sympy_s_exp_polar__ → u/rws/missing_binding_for_sympy_s_exp_polar__ 

comment:12 followup: 14 Changed 8 years ago by
Commit:  0683dd3c7f980d4a2f274a200bdcd4f69073c730 → 6d3aeaa73c6052f691a2d3cd06cd1049cc6843ff 

Milestone:  sage6.6 → sagepending 
Reviewers:  → Ralf Stephan 
Status:  new → needs_review 
Thanks for your contribution. There were some minor problems requiring changes which I have added: removed the warning (because this ticket is pending Sympy0.7.7 anyway), and adapted a bit to PEP 8. Documentation is fine, tests pass, so there is no reason to hold this back. If you agree with my changes you can set positive review.
New commits:
ef4bdb7  Merge branch 'develop' into t/18085/missing_binding_for_sympy_s_exp_polar__

6d3aeaa  18085: reviewer's patch: remove warnings, cosmetics

comment:13 Changed 8 years ago by
Status:  needs_review → positive_review 

comment:16 Changed 7 years ago by
"this ticket is pending Sympy0.7.7" (see In comment:12) but
sage: import sympy sage: sympy.__version__ '0.7.6.1'
comment:17 Changed 7 years ago by
Dependencies:  → #20185 

Report Upstream:  Fixed upstream, in a later stable release. → N/A 
comment:18 Changed 7 years ago by
Milestone:  sagepending → sage7.1 

comment:19 Changed 7 years ago by
Branch:  u/rws/missing_binding_for_sympy_s_exp_polar__ → 6d3aeaa73c6052f691a2d3cd06cd1049cc6843ff 

Resolution:  → fixed 
Status:  positive_review → closed 
The problem actually does occur in Sympy code...
Would you like to make a bug report in Sympy? Either on
Vincent