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group theory: add a check for homomorphisms from permutation groups #13151

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merged 2 commits into from Aug 29, 2017

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valglad commented Aug 18, 2017

This PR completes the method checking if given images extend to a homomorphism by adding the final case of the PermutationGroup domain.

Additionally:

  • Added _fp_presentation attribute for permutation groups because computing the presentation is time-consuming
  • Changed simpify_presentation so that the generators of the group are preserved by default. If it's desirable to remove redundant generators, the keyword change_generators can be used.
Show outdated Hide outdated sympy/combinatorics/fp_groups.py
change_gens = False
for k, v in kwargs.items():
if k == "change_gens":
change_gens = v

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@jksuom

jksuom Aug 28, 2017

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This is the recommended way of dealing with keywords that need not exist:

change_gens = kwargs.get('change_gens', False)
@jksuom

jksuom Aug 28, 2017

Member

This is the recommended way of dealing with keywords that need not exist:

change_gens = kwargs.get('change_gens', False)

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@valglad

valglad Aug 28, 2017

Contributor

I was looking for something like that, thanks.

@valglad

valglad Aug 28, 2017

Contributor

I was looking for something like that, thanks.

@jksuom jksuom merged commit 5c336d5 into sympy:master Aug 29, 2017

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@valglad valglad deleted the valglad:check_morphism branch Aug 29, 2017

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