[Maxima-bugs] [ maxima-Bugs-2859246 ] csign(log(1-%i)) --> imaginary / possible fix

[SourceForge.net <no...@so...>]

Bugs item #2859246, was opened at 2009-09-15 07:55
Message generated for change (Settings changed) made by willisbl
You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=104933&aid=2859246&group_id=4933

Please note that this message will contain a full copy of the comment thread,
including the initial issue submission, for this request,
not just the latest update.
Category: None
Group: None
Status: Open
Resolution: None
Priority: 5
Private: No
Submitted By: Barton Willis (willisbl)
Assigned to: Nobody/Anonymous (nobody)
>Summary: csign(log(1-%i)) --> imaginary / possible fix

Initial Comment:
I think this should be complex, not imaginary

(%i1) csign(log(1-%i));
(%o1) imaginary

(%i2) build_info();
Maxima version: 5.19.1
Maxima build date: 11:22 8/17/2009
host type: i686-pc-mingw32
lisp-implementation-type: GNU Common Lisp (GCL)
lisp-implementation-version: GCL 2.6.8
(%o2) 









----------------------------------------------------------------------

>Comment By: Barton Willis (willisbl)
Date: 2009-09-16 06:06

Message:
(defun sign-log (x)
  (setq x (cadr x)) ;; looking at sign of log(x)
  (cond ((eq t (meqp x 1)) (setf sign '$zero)) ;; log(1) = 0.
	;; for x in unit circle and x # 1, log(x) is pure imaginary
	((and  *complexsign* (eq 1 (meqp 1 (take '(mabs) x))) (mnqp x 1))
	 (setf sign '$imaginary))
	;; log(x) is positive for x > 1
	((eq t (mgrp x 1)) (setf sign '$pos))
	;; log(x) is negative for 0 < x < 1.
	((and (eq t (mgrp x 0)) (eq t (mgrp 1 x))) (setf sign '$neg))
	;; when *complexsign* is true, return $complex, else $pnz.
	(*complexsign* (setf sign '$complex))
	(t (setf sign '$pnz)))
  sign)

----------------------------------------------------------------------

You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=104933&aid=2859246&group_id=4933