[GAP Forum] A question.

[Alexander Hulpke]

Dear Fernando Fantino,

> I do the following, and the program give me an error.
> What happens?
> gap> Z:=Centralizer(S10,pi);
> Subgroup( Group( ( 1,10), ( 2,10), ( 3,10), ( 4,10), ( 5,10), ( 6,10),
> ( 7,10), ( 8,10), ( 9,10) ), [ ( 1, 2), ( 1, 3)( 2, 4), ( 3, 4),  
> ( 5, 6, 7),
>  ( 5, 8)( 6, 9)( 7,10), ( 8, 9,10) ] )

In GAP 3 (which you're using) defining a variable Z will destroy the  
finite field functionality and lead to weird error messages as you're  
observing. simply call the center differently (e.g. call it Y or ZZ  
or z) and things will be fine.
The same problem will arise when overwriting X or E.
In GAP4 these variables are protected against overwriting, so the  
problem cannot arise.

Best,

     Alexander Hulpke

-- Colorado State University, Department of Mathematics,
Weber Building, 1874 Campus Delivery, Fort Collins, CO 80523-1874, USA
email: hulpke at math.colostate.edu, Phone: ++1-970-4914288
http://www.math.colostate.edu/~hulpke