> < ^ Date: Mon, 09 Sep 2002 14:09:20 +0100
> < ^ From: Steve Linton <sal@dcs.st-and.ac.uk >
^ Subject: Bugfix 2 for GAP 4.3

Dear GAP Forum,

This is to announce bugfix number 2 for GAP 4.3. The priority of this fix
is high.

You should not apply this fix to any version of GAP before GAP 4.3. (If you
run such an old version, please update to GAP 4.3 (and this bugfix) as
release 4.3 corrects many problems.)

GAP Bugfixes now are comprehensive. If you forgot to install prior bugfixes,
you only need to install this, and no prior ones.

This fix corrects:

1) A segmentation fault when appending to a length 0 compressed vector
over GF2.
2) An error in the computation of inverses in quaternion algebras with
non-standard parameters.
3) The result of 'ProjectiveSymplecticGroup(n,q);'.
4) `GeneratorOfCyclicGroup' for a trivial pc group.
5) A problem in backtrack routines using `Suborbits' if the group has
fixed points in the range [1..max(Omega)].
6) A problem with `CharacterTableDirectProduct' if exactly one argument
is a Brauer table.
7) Problems with `IntScalarProduct' and `NonnegIntScalarProducts'
if the third argument is not a plain list (this situation does not occur
in GAP library functions).
8) A Problem with GQuotient
9) A problem with the linear algebra methods for Lie algebra cohomology.
10) A Problem with requesting transitive groups of degree including 1
11) A Problem with inverting lists of compressed vectors over fields
of order greater than 2.
12) An error in computing whether an element is in a Green's D equivalence
class or not.
13) A missing method for `MovedPoints(<perm>)'
14) The method IsGreensLessThanOrEqual should work for Green's D classes for
finite groups.
15) The method GroupHClassOfGreensDClass was not implemented and is required
for the Rees Matrix methods.
16) The methods AssociatedReesMatrixSemigroupOfDClass, IsZeroSimpleSemigroup,
IsomorphismReesMatrixSemigroup, and SandwichMatrixOfReesZeroMatrixSemigroup
all create Greens classes using obsolete methods which for some semigroups
leads to infinite recursion or causes GAP to stop with an error message.
17) A problem with `CentralizerModulo' for permutation groups.
18) A wrong name for PGL(2,49) in the primitive groups library of degree 50
19) An error in IdGroup
20) A missing `Representative' method for certain trivial groups.
21) A missing setting of `IndicesNormalSteps'

Error 1 causes GAP to crash.
Errors 2, 7, 18, 19 and 21 may lead to wrong results.
Error 3 GAP returned the action on lines over GF(q^2) instead of GF(q)
(which was wrong according to the documentation).
Errors 4, 5, 6, 9, 10, 11, 12, 13, 14, 15, 16, 17, and 20 will cause GAP
to stop with an error message.
Errors 8 and 16 might lead GAP to run in an infinite recursion.

Many thanks to:

Felix Noeske and Juergen Mueller for reporting problem 1.
Harm Pralle for reporting error 3.
Peter Mueller for reporting error 4.
Kurt Ewald for reporting error 5.
Kimball Martin for reporting error 8.
Ignat Soroko for reporting error 9 and 19.
James Davenport for reporting error 10.
Marco Constantini for reporting error 11.
Andrew Solomon for reporting error 12.
Andries Brouwer and Bill Thurston for reporting error 13.
J"urgen Ecker for reporting error 17.

The following errors were corrected in earlier bugfixes, which are
incorporated into this one.

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