[Maxima-bugs] [ maxima-Bugs-1313987 ] another quotient by zero bug (GCD problem)

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Bugs item #1313987, was opened at 2005-10-05 11:42
Message generated for change (Comment added) made by dgildea
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Category: Lisp Core - Polynomials
Group: None
>Status: Closed
>Resolution: Fixed
Priority: 5
Private: No
Submitted By: Barton Willis (willisbl)
Assigned to: Nobody/Anonymous (nobody)
Summary: another quotient by zero bug (GCD problem)

Initial Comment:
We have plenty of similar bug reports -- the idea 
of this bug (laplacian of algebraic & analytic must
vanish) could be a start for testing code for 
a putative fix.

(%i1) e : realpart(sqrt(1+sqrt(x+%i*y)))$
Is y positive, negative, or zero? pos;
Is sqrt(y^2+x^2) - x positive or zero? pos;

(%i2) ratsimp(diff(e,x,2) + diff(e,y,2));
`quotient' by `zero'
 -- an error.  Quitting.  To debug this try debugmode
(true);
(%i3) gcd : spmod$
(%i4) ratsimp(diff(e,x,2) + diff(e,y,2));
(%o4) 0

Barton

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>Comment By: Dan Gildea (dgildea)
Date: 2008-02-28 19:32

Message:
Logged In: YES 
user_id=1797506
Originator: NO

Fixed in rat3c.lisp rev 1.19.
Takes a long time, though.

(%i2) e : realpart(sqrt(1+sqrt(x+%i*y)))$
Is  y  positive, negative, or zero?
p;
Is  sqrt(y^2+x^2)-x  positive or zero?
p;
(%i3) ratsimp(diff(e,x,2) + diff(e,y,2)), gcd:subres;
(%o3) 0



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