Dear Forum,

Mario Pineda asked:

I am interesed on calculating the stabilizer of a point and I would be
greateful if some could help with the instructions that I need to tell
GAP(3.4 For PowerBook Mac) to do it.

To be more specific, I need to know to specify the command "opr".

<opr> is a function which defines the operation. Its syntax is
opr(<point>,<groupel>) and it should compute the image of the point under
the group element.
For standard operations there are some operations predefined: OnPoints (the
operation via ^, for example of a permutation group on points) and OnRight
(right multiplication, as a matrix group acts on a vector space).
If these specific operations are given, GAP may be able to use a better
algorithm in specific cases.

If you don't give an operation, 'OnPoints' is assumed.

So, for example:

g:=Group((1,2,3,4),(1,2));
s:=Stabilizer(g,4); returns the same as Stabilizer(g,4,OnPoints);
namely the group S3 as subgroup of S4.

Best regards,

Alexander Hulpke