#15576: Semimonomial transformation groups code is sensitive to Permutations
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Reporter: darij | Owner:
Type: defect | Status: new
Priority: major | Milestone: sage-6.1
Component: group theory | Resolution:
Keywords: permutation, | Merged in:
semimonomial transformation, | Reviewers:
groups | Work issues:
Authors: | Commit:
Report Upstream: N/A | 6155cf9ce606b77b6c70c84a106430e9068e15c2
Branch: | Stopgaps:
u/tfeulner/ticket/15576 |
Dependencies: |
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Comment (by tfeulner):
Replying to [comment:6 darij]:
> Where does `Permutation.action` depend on the multiplication order? I
agree, the function isn't very useful because it's easier to write it
oneself than to figure out what exactly it does; but it seems to be self-
contained. (It also has significant space for optimization... whoever
wrote it seems not to have realized that permutations can be iterated
over. I'll fix this in a separate ticket.)
Well, what I wanted to say is, that we need two functions to implement the
action of the permutation group on list/vectors of length `n`, depending
on the multiplication rule used for the definition of the symmetric group.
The current implementation of `Permutation.action` corresponds to the
action from the left and the multiplication defined by
`right_action_product`.
Using `left_action_product` for the multiplication in the group and still
acting from the left would force us to define the action method in the
following way:
{{{
pi * (v_1, ..., v_n) := (v_{pi^{-1}(1)}, ... , v_{pi^{-1}(n)})
}}}
But this should become the topic of a separate ticket.
Thanks for your careful reading, I think I have fixed them all.
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Ticket URL: <http://trac.sagemath.org/ticket/15576#comment:8>
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