(%o7) [b*c+a^2-a,b*d+a*b-b,c*d+a*c-c,d^2-d+b*c]
(%i8) algsys(%,[a,b,c,d]);
Maxima encountered a Lisp error:
(%i9) algsys(%o7,[a,b,c,d]),algebraic : true;
(%o9) [[a=-(sqrt(1-4*%r7*%r8)-1)/2, ...]]
Would it be OK to have algsys (or maybe just resultant)
set algebraic to true?
Barton
Barton Willis
2006-02-13
Logged In: YES
user_id=895922
Proposed fix:
(defmfun $resultant (a b mainvar)
(prog (varlist formflag $ratfac res ans genvar $keepfloat
$algebraic)
(setq varlist (list mainvar) $ratfac t ans 1 $algebraic t)
It seems to fix the problem:
(%o9) [b*c+a^2-a,b*d+a*b-b,c*d+a*c-c,d^2-d+b*c]
(%i10) algsys(%,[a,b,c,d]);
(%o10) [[a=-(sqrt(1-4*%r7*%r8)-1)/2,b=%r7
Barton
Robert Dodier
2006-08-15
Logged In: YES
user_id=501686
Observed in 5.9.3.99rc1.
Robert Dodier
2006-08-15
Robert Dodier
2006-09-08
Robert Dodier
2006-09-09
Dieter Kaiser
2009-01-25
This bug reported is related to the bug report SF[609466].
A check for a number zero in a call to punivarp has been checked in.
Maxima no longer gets a fatal Lisp error for the examples given in this bug report, but returns an error message:
`algsys' cannot solve - system too complicated.
-- an error. To debug this try debugmode(true);
Should we close the bug report too? The Lisp error has gone. The algorithm is not smart enough to find a solution for the problem, but that might be not a bug.
To improve algsys more general we can set the flag $algebraic in the routine $algsys. That is the point a lot of global variables are set.
Dieter Kaiser
Dieter Kaiser
2010-02-10
Dieter Kaiser
2010-02-10
The Lisp error has gone as written in the last posting.
The system is solveable with the option variable algebraic set to true:
(%i1) [b*c+a^2-a,b*d+a*b-b,c*d+a*c-c,d^2-d+b*c];
(%o1) [b*c+a^2-a,b*d+a*b-b,c*d+a*c-c,d^2-d+b*c]
(%i2) algsys(%,[a,b,c,d]),algebraic:true;
(%o2) [[a = -(sqrt(1-4*%r559*%r560)-1)/2,b = %r559,c = %r560,
d = (sqrt(1-4*%r559*%r560)+1)/2],
[a = (sqrt(1-4*%r561*%r562)+1)/2,b = %r561,c = %r562,
d = -(sqrt(1-4*%r561*%r562)-1)/2],[a = 0,b = %r563,c = 0,d = 1],
[a = 1,b = %r564,c = 0,d = 0],[a = 1,b = 0,c = 0,d = 1],
[a = 0,b = 0,c = 0,d = 0]]
I think we no longer have a bug. Setting the status to pending and the resolution to "works for me".
Dieter Kaiser
SourceForge Robot
2010-02-25
SourceForge Robot
2010-02-25
This Tracker item was closed automatically by the system. It was
previously set to a Pending status, and the original submitter
did not respond within 14 days (the time period specified by
the administrator of this Tracker).