#6523: .is_zero() method raises error for symbolic expression involving
derivative
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Reporter: gmhossain | Owner:
Type: defect | Status: new
Priority: major | Milestone: sage-4.1.1
Component: symbolics | Keywords:
Reviewer: | Author:
Merged: |
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Changes (by burcin):
* cc: mhansen (added)
* milestone: => sage-4.1.1
Comment:
Unfortunately, the fact that an expression contains a symbolic derivative
doesn't guarantee that it is nonzero:
{{{
sage: t = f(x).derivative(x)
sage: (x*t +(1-x)*t - t)
-(x - 1)*D[1](f)(x) + x*D[1](f)(x) - D[1](f)(x)
sage: (x*t +(1-x)*t - t).collect(x)
0
}}}
The right fix for this is to either implement the `.derivative()` method
in `sage/symbolic/expression_conversions.py` or to change pynac to allow
different parents in `evalf()`, so that conversion to `CIF` can be done
without the code in `expression_conversions.pyx`.
I was planning to do this for #6243, but ended up using a different/better
fix there.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/6523#comment:2>
Sage <http://sagemath.org/>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
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