Opened 11 years ago

Last modified 5 years ago

#9424 closed defect

numerical evaluation of symbolic sums — at Initial Version

Reported by: burcin Owned by: burcin
Priority: major Milestone: sage-6.8
Component: symbolics Keywords:
Cc: whuss, kcrisman, eviatarbach Merged in:
Authors: Reviewers:
Report Upstream: N/A Work issues:
Branch: Commit:
Dependencies: Stopgaps:

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Description

Symbolics sums returned from maxima cannot be numerically evaluated, since they don't define an _evalf_() method.

This was reported by dirkd on sage-support:

Why is evaluating this expression problematical?

y1(x)=x^2;y2(x)=5-x;
a0=1;an=3;Delta=(an-a0)/n;p(k)=a0+(k-1/2)*Delta;
I(n)=sum(abs(y2(p(k))-y1(p(k)))*Delta,k,1,n);
N(I(10))

SAGE respons:
<snipped traceback>
  File "expression.pyx", line 3797, in
sage.symbolic.expression.Expression.n (sage/symbolic/expression.cpp:
17022)
TypeError: cannot evaluate symbolic expression numerically

Here is the thread:

http://groups.google.com/group/sage-support/t/615b15ca638c9652

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