>
> Are you suggesting that things such as Permutation([x,y,z]) work?
>
Yes.
> If so, I will think that will cause more problems than it is worth -- in
> fact, it isn't really well-defined. A permutation is a boijection
> from a set to itself. The one-line permutation notation requires a
> total ordering for the set. For example, without a ordering on
> {x,y,z}, there isn't any way to make sense of Permutation([z,y,x]) *
> Permutation([y,z,x]). If you really want to have permuations on sets
> other than {1,...,n}, then you'll either need to make explicit the
> underlying set.
>
Not sure I follow. It is indeed a bijection of a set to itself, but under
the assumption that each element is a unique Expr object couldn't the
one-line permutation notation be given? Even with assumption-free variables
SymPy has a canonical way of ordering things, no?
So there may be further assumptions (not in the SymPy sense) that are
placed on the elements passed in (e.g., uniqueness), but that's what I'm
hoping to flesh out in this discussion.
Cheers,
Christian
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