On 17-Mar-10, at 10:12 PM, Jason Grout wrote:
On 03/17/2010 11:40 AM, Nick Alexander wrote:
On 17-Mar-10, at 10:18 AM, Mike Hansen wrote:
On Wed, Mar 17, 2010 at 5:21 AM, Pablo Angulo <pablo.ang...@uam.es>
wrote:
Sorry to come back to this (two weeks) old topic, but what do you
think
about raising an exception whenever a symbolic integral (or any
symbolic
computation) fails? Otherwise, is there a simple way to
distinguish a
succesful integration from failed ones that are just indicated
(e.g.,
integrate(e^(x*sin(x)), x))?
You can check whether or not you get an unevaluated integral like
this:
sage: f = integrate(x^2, x)
sage: isinstance(f.operator(),
sage.symbolic.integration.integral.IndefiniteIntegral)
False
sage: f
1/3*x^3
sage: f = integrate(e^(x*sin(x)), x)
sage: isinstance(f.operator(),
sage.symbolic.integration.integral.IndefiniteIntegral)
True
sage: f
integrate(e^(x*sin(x)), x)
Using isinstance is such a strong code smell. Maybe we should add
some
interrogation routines, is_definite_integral/
is_indefinite_integral/...?
Are you saying every symbolic expression should have an
is_indefinite_integral method? That seems a little clumsy to me; I
must be misunderstanding what you are proposing. What other
interrogation methods should be added if that is what you are
proposing. Obviously a person could get carried away, adding an
is_addition, for example.
At the time I worked with this code, which was several months ago,
there was no public interface for crawling the structures. Testing
for whether one was looking at a sage value (meaning something with a
parent) versus a function application versus a derivative was really
hard. When you have one very general "expr" class, how else do you
determine if you're looking at an indefinite integral? (Or an
addition, for that matter?)
Nick
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