[Axiom-developer] [#212 substituting for an operator in a sum does not apply the summation algorithms] (new) substituting for an operator in a sum does not apply the summation algorithms

[Bill Page]

Changes 
http://page.axiom-developer.org/zope/mathaction/212SubstitutingForAnOperatorInASumDoesNotApplyTheSummationAlgorithms/diff
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Update of bug #9217 (project axiom):

                  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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