# Axiom Computer Algebra System - Bugs: bug #9217, substituting for an operator in a...

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*bug #9217*: substituting for an operator in a sum does not apply the summation algorithms

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Date | Changed by | Updated Field | Previous Value | => | Replaced by |
---|---|---|---|---|---|

2005-10-03 | billpage1 | Status | None | transferred | |

Internal cause | first the sum is evaluated. Since the argument -- f(x)-- is not a polynomial or rational function, using first iidsum, than idsum of COMBF. Afterwards the substitution is performed. Now the sum has the internal format %defsum [%A, %A, i, a, b], which is again evaluated with iidsum and idsum of COMBF. The function sum$InnerPolySum is never called, of course. A general solution is to call sum from within idsum, but in this case, care has to be taken that summation algorithms that can fail (such as Gosper's) do not produce an infinite loop. (In fact I think this is OK, I only did not have the time to check) | first the sum is evaluated. Since the argument -- f(x)-- is not a polynomial or rational function, using first iidsum, than idsum of COMBF. Afterwards the substitution is performed. Now the sum has the internal format %defsum [%A, %A, i, a, b], which is again evaluated with iidsum and idsum of COMBF. The function sum$InnerPolySum is never called, of course. A general solution is to call sum from within idsum, but in this case, care has to be taken that summation algorithms that can fail (such as Gosper's) do not produce an infinite loop. (In fact I think this is OK, I only did not have the time to check) |

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