Dear Forum,

This is to announce bugfix number 6 for GAP 4.2. The priority of this fix
is very high.

You should not apply this fix to any version of GAP3, nor to any
version of GAP4.1.

This fix corrects:

1) Wrong generators for General and Special Orthogonal Groups
2) A bug in `SimpleLieAlgebra' for type G.
3) A bug in inverting compressed matrices over non-prime fields of
characteristic 2
4) A bug in PcgsElementaryAbelianSeries and CentralizerModulo
5) An bug in the resultant routine for polynomials.
6) A bug in the element test routine for subfields of algebraic extensions.
7) Wrongly stored ``is sorted'' after sorting with a special ordering function.
8) A bug in `AdjointBasis' for Lie Algebras.
9) A bug in the composition series routine for permutation groups.
10) A bug in the stabilizer chain routine for groups that are known to be
solvable (a specified base might not be guaranteed).

Errors 3,5,6,7,9,10 may cause GAP incorrect results in calculations involving
these routines.
Error 1 may lead to wrong generators and inconsistent group for orthogonal
groups obtained via `GeneralOrthogonalGroup' and `SpecialOrthogonalGroup'.
Errors 2,4 and 5 can cause GAP to stop with an error message or without
returning a result.

Many thanks to:
Stefan Kohl for reporting error 2.
Nicola Sottocornola for reporting error 6.
Marco Costantini for reporting error 8.
Burkhard H"ofling for the new Macintosh Binaries.

Installing the bugfix.
======================

Please note that it might take a few days for the mirrors to pick up the
bugfix files. Also, the mentioned binaries for Windows and Macintosh will be
available only in a few days time.

Load the zoo archive `fix4r2n6.zoo' from the bugfixes web page
http://www-gap.dcs.st-and.ac.uk/~gap/Info4/bugfixes.html
Alternatively you can find this file in the `bugfixes' directory of the
GAP4 ftp distribution.

Unpack the file in the home directory of your GAP distribution (the
directory containing the `lib' and `grp' directories) using `unzoo -x
fix4r2n6.zoo'. `unzoo' may ask you for permissions to overwrite files,
answer this with Y)es or A)ll. This will replace the erroneous files by
fixed versions.

(On a PC or a Mac you will have to copy `unzoo' in the same directory and
enter the argument line after the call to `unzoo'.)
Make sure you have write permissions when applying the fix.

You can remove the file `description6' afterwards.
This fix changes the kernel. You have to recompile by calling `make' in the
directory in which you unpacked the fix.

Windows users can find a new binary in the file `wbin4r2n6.zoo' in the
`bugfixes' directory: Extract this archive in the same place as the fix
archive to get a new `gapw95.exe' file.

Macintosh users should download the file 'bin4r2n6-PPC.sit' (for PPC
machines) or 'bin4r2n6-68k.sit' (for 68k machines), from the 'bugfixes'
directory.

If you get one of these precompiled binaries you do not need to get any
precompiled binaries that would have come with earlier fixes (these old
binaries are obsolete now). Similarly, if you cannot find these binaries but
have further, newer, fixes to install check whether new binaries with these
fixes did not make the binaries of this fix obsolete.

After installing the bugfix you can test whether
the bugfix has been applied correctly by starting GAP from the `gap4r2'
directory and issuing

gapReadTest("tst/bugfix.tst");
+ bugfixes test
+ GAP4stones: 835
true

(The output should be like this if the bugfixes have been installed
correctly. The number of GAP4stones may vary according to your system.)

Alexander Hulpke and Steve Linton, 26.Jan.2001