[Maxima-bugs] [ maxima-Bugs-2423045 ] simpsum yields incorrect results

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Bugs item #2423045, was opened at 2008-12-12 20:31
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Category: Lisp Core - Simplification
Group: None
Status: Open
Resolution: None
Priority: 7
Private: No
Submitted By: Viktor Toth (vttoth)
Assigned to: Nobody/Anonymous (nobody)
Summary: simpsum yields incorrect results

Initial Comment:
The following gives an incorrect result:

sum(i,i,q,n),simpsum;

First, it invokes asksign for q, which is unnecessary. Second, if the user specifies q as negative, the result given is, (n^2+n)/2-(q^2+q)/2, which is incorrect (the correct result is the same that is given when q>=0, as can be verified by hand.)

Robert Dodier suggests that the problem may be due to some strangeness in polysum, which is defined in combin.lisp.

As in this case, a mathematically incorrect result is produced, I mark this error with a high priority.


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