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: |

### 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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