[GAP Forum] what does "." and "=" mean in StructureDescription?

[Will Chen]

A good example is AllSmallGroups(96,191), which seems to have
StructureDescription:

"(C2.S4=SL(2.3).C2):C2"

I understand that the colon ":" denotes semidirect product, so this is the
semidirect product of something with the cyclic group of order 2.

Here is C2 the normal subgroup of the semidirect product? Does the normal
subgroup always appear on the right?

What about the rest? Since the whole group has order 96, the stuff on the
left of the ":" must have order 48, so I can only assume that the "=" means
"or equivalently...". Is that correct?

In this case, I'm guessing "." refers to a non-split extension? If I see
G.H, which is the normal subgroup?

Thanks,

- Will

-- 

William Yun Chen
Ph.D. Student & Graduate Teaching Associate
Department of Mathematics
Pennsylvania State University, University Park, PA, 16801
chen_w at math.psu.edu
oxeimon at gmail.com