Dear GAP-Forum,

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

This fix corrects:
1) An error in the 'PreImagesRepresentative' code for homomorphisms between
AgGroups.
2) An error in the 'Centralizer' code for AgGroups that may introduce
duplicate parent groups.
3) An error in 'RealClassesCharTable'.
4) A compiler problem in the DOS version. (With level 2 optimization the
Kernel function TreeEntry does not work.)
5) Potentially stray pointers in kernel routines for finitely presented
groups if a garbage collection is issued in between.
6) Adaption of the XGAP share package to changes in the Tietze transformation
routines in GAP 3.4.4
7) Upgrade of the MeatAxe share package to the C-Meataxe 2.2.3 (to avoid
problems under Linux)

Errors 1 and 3 may give wrong results, errors 2 may cause GAP to
issue an error message. Error 4 will lead to unpredictable results (wrong
results of error messages).
Error 5 might possibly lead to segmentation faults.

Many thanks to Martyn Quick for (implicitly) reporting error 1, to Gerhard Hiss
for reporting error 3 and to Charles Leytem for reporting error 4.

To apply the fix, load the zoo archive 'fix7.zoo' from the
bugfixes web page
http://www-gap.dcs.st-and.ac.uk/~gap/Info/bugfixes.html
Alternatively you can find this file in the 'bugfixes' directory of the
GAP ftp distribution.

Unpack the file in the home directory of your GAP distribution (the
directory containing the 'lib' and 'etc' directories) using 'unzoo -x
fix7.zoo' (On a PC or a Mac you will have to enter the argument line after
the call to 'unzoo'.) This will replace the erraneous file by fixed versions.
Make sure you have write permissions when applying the fix.

As this fix changes the source you will have to recompile. DOS and MAC
users will find new binaries on the bugfixes web page.

If you use the MeatAxe share package you will also have to recompile the
MeatAxe binaries.

You can remove the file 'description7' afterwards.

Thomas Breuer, Frank Celler, Volkmar Felsch, Alexander Hulpke,
and Werner Nickel, 12-Sep-97

#############################################################################
#
# these commands should run without error if fix7 has been applied.
#
g:= SmallGroup( 36, 1 );
gens:= g.generators;
a:= gens[1];;
b:= gens[2];;
c:= gens[3];;
d:= gens[4];;
bad:= a*b*c^2*d^2;;
c1:= Centralizer( g, b );
c2:= Centralizer( c1, a );
c3:= Centralizer( c2, bad );
DoubleCosets( g, c1, c2  );
DoubleCosets( g, c1, AsSubgroup( g, c3 ) );
DoubleCosets( g, c1, c3 );

g:=TransitiveGroup(12,200);
a:=AgGroup(g);
cl:=List(ConjugacyClassesSubgroups(a),Representative);
z:=First(cl,i->Size(i)=96);
m:=AgGroup(z);
imgs:=List(z.generators,
i->Image(m.bijection,PreImagesRepresentative(m.bijection,i))/i);
if ForAny(imgs,i->i<>a.identity) then
Error("fails!");
fi;

c:=FreeGroup(4,"c");
r:=List(c.generators,x->x^2);
Append(r,[(c.1*c.2)^4,(c.1*c.3)^2,(c.1*c.4)^2,(c.2*c.3)^4,
(c.2*c.4)^2,(c.3*c.4)^4]);
Append(r,[(c.1*c.2*c.3*c.2)^3,(c.2*c.3*c.4*c.3)^5]);
c:=c/r;
s:=Subgroup(c,[c.3*c.1,c.4*c.2,c.1*c.4*c.2*c.1]);
p:=PresentationSubgroup(c,s);