log(neg integer) not fully simplified/fix

[rtoy]

Imported from SourceForge on 2024-07-04 20:13:46 Created by willisbl on 2005-12-03 20:09:55 Original: https://sourceforge.net/p/maxima/bugs/829

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(%i1) declare(n,integer); (%o1) DONE (%i2) assume(n > 0); (%o2) [n>0] (%i3) log(-n^2), lognegint, logexpand;

An extra log expand is needed:

(%o3) log(n^2)+%i*%pi (%i4) %,logexpand; (%o4) 2*log(n)+%i*%pi

A putative fix; in simpln, replace

(add2 '((mtimes simp) $%i $%pi) (cond ((equal y -1) 0) (t (list '(%log simp) (neg y))))))

with something like

(and $lognegint (maxima-integerp y) (eq ($sign y) '$neg)) (add (mul '$%i '$%pi) (take '(%log) (neg y))))

If both ($sign y) and ($sign (neg y)) evaluate to '$neg, we're toast. But that would never happen...

Barton

[rtoy]

Imported from SourceForge on 2024-07-04 20:13:47 Created by robert_dodier on 2006-08-15 02:43:10 Original: https://sourceforge.net/p/maxima/bugs/829/#50f2

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• labels: --> Lisp Core - Simplification

[rtoy]

Imported from SourceForge on 2024-07-04 20:13:51 Created by robert_dodier on 2006-08-15 02:43:10 Original: https://sourceforge.net/p/maxima/bugs/829/#4264

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Logged In: YES user_id=501686

Observed in 5.9.3cvs.

[rtoy]

Imported from SourceForge on 2024-07-04 20:13:54 Created by robert_dodier on 2006-09-09 15:10:57 Original: https://sourceforge.net/p/maxima/bugs/829/#9960

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• milestone: --> Includes_proposed_fix

[rtoy]

Imported from SourceForge on 2024-07-04 20:13:57 Created by willisbl on 2008-03-09 12:45:19 Original: https://sourceforge.net/p/maxima/bugs/829/#7d68

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Logged In: YES user_id=895922 Originator: YES

Fixed by simp.lisp cvs revision 1.53.

[rtoy]

Imported from SourceForge on 2024-07-04 20:14:01 Created by willisbl on 2008-03-09 12:45:19 Original: https://sourceforge.net/p/maxima/bugs/829/#c4d3

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• status: open --> closed