Dear Forum,

This is to announce bugfix number 7 for GAP 4.2. The priority of this fix
is high.

You should not apply this fix to any version of GAP3, nor to any
version of GAP 4.1.

This fix corrects:

1) A parent group set too small when centralizing a subgroup of a pc group.
2) An error in the tietze transformation routines.
3) Lists incorrectly remembering themselves to be non-sorted, even
after sorting
4) `PcgsElementaryAbelianSeries' not storing that the pcgs is a prime orders
pcgs.
5) A problem in `IsomorphicSubgroups' for groups which cannot be generated
by two elements.
6) A problem with computing pcgs for permutation groups if a partial
stabilizer chain is known.
7) A problem with `RepresentativeTomByGenerators' for fetching a trivial
group.
8) An error in the `Display' method for straight line programs.
9) A problem with vector spaces consisting of field elements.

Errors 1, 4, 6, 7, and 9 may cause GAP to stop with an error message.
Errors 2 and 5 can cause GAP to run in an infinite loop.
Errors 3 and 8 could cause wrong results.

Many thanks to:
Toshio Sumi for reporting errors 1 and 2.
Len Soicher for reporting error 3.
Peter Mueller for reporting error 4.
Stefan Kohl for reporting errors 1, 5, and 6.
Klaus Lux for reporting errors 7 and 9.

Burkhard H"ofling for the new Macintosh Binaries.

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

Load the zoo archive `fix4r2n7.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
fix4r2n7.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 `description7' 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 `wbin4r2n7.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 'bin4r2n7-PPC.sit' (for PPC
machines) or 'bin4r2n7-68k.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

gap> ReadTest("tst/bugfix.tst");
+ bugfixes test
+ GAP4stones: 31415
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, Mar 5, 2001