This mail contains a bugfix for a serious problem in GAP 3.4.3.
You should apply this bugfix soon if you are computing with polynomials.
The problem is in 'StandardAssociate' for polynomials, and causes it to
fail for the 0 polynomial.

HOW TO APPLY

The problem is a serious problem, because it may cause a computation to
fail. Thus the bugfix has medium priority, and we recommend that you
apply it soon if you are computing with polynomials.

Go to the GAP directory (the directory with the 'lib/' subdirectory),
name this mail 'bugfix06.dif', and issue the command:

patch -p0 < bugfix06.dif

This workaround changes only the library. Thus you need not recompile
the GAP kernel.

VERSION

GAP 3.4.3.0

DESCRIPTION

'StandardAssociate' fails for the 0 polynomial and signals

Error, List Element: <position> must be a positive integer at
return f * f.coefficients[Length( f.coefficients )] ^ (-1 * 1) ... in
R.operations.StandardAssociate( R, r ) called from
StandardAssociate( 0 * x ) called from
main loop

CORRECT BEHAVIOUR

gap> x := X(Rationals);;
gap> StandardAssociate( 0 * x );
0*X(Rationals)^0

COMMENT

Harald Boegeholz mailed a bugfix for this problem in 1994/04/17.
That means it was available *before* GAP 3.4.0 was released,
and still it did not make it into GAP 3.4.3.

PATCH

Prereq: 3.9
--- lib/polyfld.g       1994/06/10 02:44:03
+++ lib/polyfld.g       1996/04/03 13:24:53
@@ -2,13 +2,16 @@
 ##
 #A  polyfld.g                   GAP library                      Frank Celler
 ##
-#A  @(#)$Id: 1.html,v 1.2 2004/04/21 15:06:18 felsch Exp $
+#A  @(#)$Id: 1.html,v 1.2 2004/04/21 15:06:18 felsch Exp $
 ##
 #Y  Copyright 1990-1992,  Lehrstuhl D fuer Mathematik,  RWTH Aachen,  Germany
 ##
 ##  This file contains functions for polynomials over fields.
 ##
 #H  $Log: 1.html,v $
 #H  Revision 1.2  2004/04/21 15:06:18  felsch
 #H  Corrected links in the Forum Archive pages.   VF
 #H
 #H  Revision 1.1.1.1  2004/04/20 13:39:30  felsch
 #H  The final GAP-Forum archive until 2003.
 #H
 #H  Revision 1.5  2003/06/12 19:20:33  gap
 #H  Further update. AH
 #H
 #H  Revision 1.4  2003/06/12 17:28:25  gap
 #H  Address updates by JN. AH
 #H
 #H  Revision 1.3  1997/08/15 11:19:33  gap
 #H  New forum setup. AH
 #H
 #H  Revision 1.2  1997/04/24 15:32:47  gap
 #H  These files were replaced by the versions in WWW. The content is basically the
 #H  same but the formatting has been much more friendly towards the HTML-Converter.
 #H  AH
 #H
 #H  Revision 1.1  1996/10/30 13:07:04  gap
 #H  added forum archive and translation files.
 #H
+#H  Revision 3.9.1.1  1996/01/08  15:20:53  ahulpke
+#H  fixed 'StandardAssociate' for 0
+#H
 #H  Revision 3.9  1994/06/10  02:44:03  sam
 #H  fixed 'EuclideanQuotient'
 #H
@@ -58,6 +61,9 @@
 #F  FieldPolynomialRingOps.StandardAssociate( <R>, <f> )  . . . .  normed pol
 ##
 FieldPolynomialRingOps.StandardAssociate := function( R, f )
+    if Length(f.coefficients)=0 then
+      return Zero(R);
+    fi;
     return f * f.coefficients[ Length( f.coefficients ) ]^-1;
 end;

END OF  bugfix06.dif ________________________________________________________