axiom-developer
[Top][All Lists]

[Axiom-developer] [#212 substituting for an operator in a sum does not a

 From: billpage Subject: [Axiom-developer] [#212 substituting for an operator in a sum does not apply the summation algorithms] Date: Mon, 03 Oct 2005 01:21:10 -0500

Changes
http://wiki.axiom-developer.org/212SubstitutingForAnOperatorInASumDoesNotApplyTheSummationAlgorithms/diff
--

??changed:
-
-
-From BillPage Mon Oct 3 01:08:57 -0500 2005
-From: Bill Page
-Date: Mon, 03 Oct 2005 01:08:57 -0500
-Subject: (new) substituting for an operator in a sum does not apply the
-       summation algorithms
-
-
-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$InnerPolySum is never called, of course. A general Original Savannah bug 9217 Summary: Although axiom can evaluate this sum, it does not. Example of code trigerring the bug: \begin{axiom} f := operator 'f sum(f(i),i=a..b) eval(%,f,x+->x) \end{axiom} Internal Cause first the sum is evaluated. Since the argument 'f(x)' is not a polynomial or rational function, using first iidsum, than idsum of COMBF. Afterwards the substitution is performed. Now the sum has the internal format '%defsum [%A, %A, i, a, b]', which is again evaluated with iidsum and idsum of COMBF. The function 'sum$InnerPolySum' is never called, of course. A general

??changed:
-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)
-
-
-    _______________________________________________________
-
-
-  <http://savannah.nongnu.org/bugs/?func=detailitem&item_id=9217>
-
-_______________________________________________
-[2 more lines...]
the time to check)

--