Ha! And another implementation of the hierarchical #FSM copes with the same calculator without duplicating the code (more precisely, it's still there, but on a smaller scale and is localized).
The thing is that in the former machine, the in_enter() mechanism was implemented through a simple ON_ENTER event, which automatically destroyed all traces of the event that led to this very enter😉
"I appreciate SDF but it's a general-purpose server and the name doesn't make it obvious that it's about art." - Eugen Rochko