Problem Description

Reversion of combinatorial species is inherently slow, but at least for the case of the species of non-empty sets the reversion is known.

The same holds for LazySymmetricFunctions. Note that species.generating_series.LogarithmCycleIndexSeries in fact implements a faster version.

Proposed Solution

From #38544:

Note to myself: Labelle 2013 has an explicit expression for molecular expansion of the combinatorial logarithm, i.e., L.Sets().restrict(1).revert(), and also for compositions of this with an arbitrary species.

I don't know yet how to best integrate this into the framework. Maybe revert could detect this special case, or we could learn from this special case how to make revert fast.

Alternatives Considered

Either make revert fast, or implement the special cases.

Additional Information

No response

Is there an existing issue for this?

• I have searched the existing issues for a bug report that matches the one I want to file, without success.