> < ^ Date: Mon, 13 Nov 2000 15:51:53 +0100 (MET)
< ^ From: Laurent Bartholdi <Laurent.Bartholdi@math.unige.ch >
> ^ Subject: other problems with gap

hello again,
i ran in a few new other problems with gap, which are:

i cannot define a group algebra over an infinite non-free group:
gap> G := FreeGroup("a","b");
<free group on the generators [ a, b ]>
gap> GroupRing(GF(2),G);
<algebra-with-one over GF(2), with 4 generators>
gap> G := G / [Comm(G.1,G.2)];
<fp group on the generators [ a, b ]>
gap> GroupRing(GF(2),G);
Error the coset enumeration has defined more than 256000 cosets:

and also i can't run ReducedConfluentRewritingSystem on a f.p. group --
gap wants a f.p. semigroup. i would have thought AsSemigroup(G) would
work, but alas not.

concerning coset enumeration, couldn't it be possible to set up a flag in
a group structure that the group is infinite, so that gap does not attempt
element or coset enumeration, but rather answers by an error message?

cheers all,

[p.s. to derek holt: yes, i saw your message. it gave me courage to clog
gap-forum with my problem, since it obviously is something of great

``a theorem is a device for turning mathematicians into coffee'' -- not Erdös
E-Mail: mailto:laurent.barth0ldi@math.unige.ch (replace 0 by o)
S-Mail: Laurent Bartholdi, 15 Bvd de la Cluse, 1205 Genève, Switzerland
Office: #610B, 2-4 Rue du Lièvre, Case Postale 240, 1211 Genève 24, Switzerland
Phones: +41 78 7480012 (mobile) +41 22 3280012 (home) +41 22 3095437 (office)

> < [top]