[GAP Forum] bag with IsomorphismPermGroup

[Evgeny Vdovin]

Dear all,
This program runs ok on my GAP

F:=FreeGroup(1);
G:=F/[F.1^5];    # Z_5
h:=NqEpimorphismNilpotentQuotient(G,1);;
H:=Image(h);
Size(H);    # critical line
IsomorphismPermGroup(H);

but if I remove the "critical line"

F:=FreeGroup(1);
G:=F/[F.1^5];    # Z_5
h:=NqEpimorphismNilpotentQuotient(G,1);;
H:=Image(h);
IsomorphismPermGroup(H);

it runs into error as follows:


gap> F:=FreeGroup(1);
<free group on the generators [ f1 ]>
gap> G:=F/[F.1^5];    # Z_5
<fp group on the generators [ f1 ]>
gap> h:=NqEpimorphismNilpotentQuotient(G,1);
[ f1 ] -> [ g1 ]
gap> H:=Image(h);
Pcp-group with orders [ 5 ]
gap> IsomorphismPermGroup(H);
Error, no method found! For debugging hints type ?Recovery from
NoMethodFound
Error, no 2nd choice method found for `IsomorphismPermGroup' on 1
arguments called from
<function>( <arguments> ) called from read-eval-loop
Entering break read-eval-print loop ...
you can 'quit;' to quit to outer loop, or
you can 'return;' to continue
brk>

I have no idea why choosing not to calculate Size(H) makes the program
break.
Can anyone help me out?


-- 
Best Regards
Prof. Vdovin Evgeny
Institute of Mathematics
pr-t Acad. Koptyug, 4
630090, Novosibirsk, Russia
Office    +7 383 3634540
Cellular  +7 913 9475524
Fax       +7 383 3332598