[isabelle-dev] Permutations

Florian Haftmann florian.haftmann at informatik.tu-muenchen.de
Tue Jul 5 20:02:14 CEST 2016

> What about adding it to the ab_group_add typeclass? I know this is not
> the usual mathematical syntax for permutations, but at least we can
> reuse a lot of theorems from this type class.

There *is* reuse since there is a separate interpretation of the
abstract ab_group locale.

I once met an algebraist who preferred + for abelian groups and *
otherwise, and this makes sense.


>  - Johannes
> Am Dienstag, den 05.07.2016, 19:40 +0200 schrieb Florian Haftmann:
>>> One question: why did you only set it up for monoid_mult and
>>> inverse,
>>> and not as a ab_group_mult?
>> The answer is simple: there is no type class
>> ab_group_mult.  Why?  Since
>> our multiplicative structures are tailored towards rings where 0 is
>> no
>> part of the multiplicative group.
>> Cheers,
>> 	Florian


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