[Maxima-bugs] [ maxima-Bugs-2824047 ] sum(x,x,-a,0); wrong

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Bugs item #2824047, was opened at 2009-07-19 20:01
Message generated for change (Settings changed) made by willisbl
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https://sourceforge.net/tracker/?func=detail&atid=104933&aid=2824047&group_id=4933

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Category: None
Group: None
>Status: Closed
>Resolution: Fixed
Priority: 5
Private: No
Submitted By: Nobody/Anonymous (nobody)
Assigned to: Nobody/Anonymous (nobody)
Summary: sum(x,x,-a,0); wrong

Initial Comment:
Summary:  sum(...,x,-a,0) is wrong when the first argument is a polynomial in x, a is unbound,
and you respond to "Is  a  positive, negative, or zero?" with positive.

Example:
(%i1) sum(x,x,-a,0);
p;
(%o1) -(a^2-a)/2

The result should be -(a^2+a)/2.

Negative numeric limits work fine:
(%i1) sum(x,x,-5,0);
(%o1) -15

Evaluating the incorrect result of (%i1):
(%i2) subst(5,a,%o1);
(%o2) -10

Evaluating the correct formula:
(%i3) -(5^2+5)/2;
(%o3) -15


Maxima version: 5.13.0
Maxima build date: 9:20 12/12/2007
host type: i686-pc-linux-gnu
lisp-implementation-type: GNU Common Lisp (GCL)
lisp-implementation-version: GCL 2.6.8



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>Comment By: Barton Willis (willisbl)
Date: 2009-07-20 20:21

Message:
Thanks for the bug report.  This bug was fixed just recently:

(%i1) display2d : false$
(%i2) sum(x,x,-a,0),simpsum$
(%i3) factor(%);
(%o3) -a*(a+1)/2
(%i4) build_info();

Maxima version: 5.18post
Maxima build date: 16:1 7/8/2009
host type: i686-pc-mingw32
lisp-implementation-type: Clozure Common Lisp
lisp-implementation-version: Version 1.4-dev  (WindowsX8632)



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You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=104933&aid=2824047&group_id=4933