# [GAP Forum] ? trouble getting started ?

Marco Costantini costanti at science.unitn.it
Mon Jul 26 14:06:39 BST 2004

```Dear Brian Beckman and dear Gap-forum,

> I could not figure out
> "multiplication" of purmutations, however, so (1,2)*(1,2,3)=(1,3); did
> not
> make sense to me and (1,2,3)*(1,2)=(2,3); did not make sense. I expected
> (1,2)*(1,2,3)=(1,2,3)^(1,2) and (1,2,3)*(1,2)=(1,2)^(1,2,3), but that's
> obviously not the case.

You can think the permutations as elements of a opportune permutation group,
and the composition of permutation as the group operation. As usually the
group operation is called "multiplication" and is denoted by "*", it is
natural to call "multiplication"  also the composition of permutations, and
to use "*" in Gap, where only a limited set of symbols is available.

> I apologize for my ignorance of the subject, but I am attempting to use
> GAP
> to learn algebra.

Welcome to using Gap and to learn algebra!

Please feel free to ask in case that you need further help. There is the
address support at gap-system.org to deal with those topics that are more or
less local to you, that is, are likely not of interest to most of the other
GAP users.

On the other hand, the GAP Forum should be reserved for discussions about
problems that are likely to interest many of the GAP users.

Best regards,
Marco Costantini

```

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