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Steve Fisk writes in his e-mail message of 21-Apr-92

I wish to determine the size of many (3*12^4) groups. These groups

are given by generators (4 generators) and relations (16 relations).

It was very easy to program it, and I was surprised to see that all

the groups had order 2. I suspected an error, and found it in

Chapter 21: you can not change the generators of a group! I had

fixed one group and just kept changing its generators.

Changing the generators (or relators) of a group after any computation

has been performed with this group is not allowed. What probably happens

in this case is that after the first computation the group has the

component 'g.size' (with the value 2), and subsequent calls to 'Size'

will only return this value.

Steve Fisk continues

I do not see how to get around this problem, except by writing an AWK

program to write 3*12^4 gap programs, and execute them, but there

must be a better way.

I am not certain that I understand your problem fully. But the following

code defines a number of groups and computes the size of each. Does this

do what you want?

gap> sizes := []; gap> for i in [4..10] do > g := FreeGroup( 2, "g" ); > g.relators := [ g.1^2, g.2^2, (g.1*g.2)^i ]; > Add( sizes, Size( g ) ); > od; gap> sizes; [ 8, 10, 12, 14, 16, 18, 20 ]

Martin.

--

Martin Sch"onert, Martin.Schoenert@Math.RWTH-Aachen.DE, +49 241 804551

Lehrstuhl D f"ur Mathematik, Templergraben 64, RWTH, D 51 Aachen, Germany

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