A BaseStateMachine currently uses a Topology that encodes its valid transitions in a list.

To aid in the construction of some state machines, we implicitly allow identity transitions (#13). However, we are unable to model state machines without identity transitions.

We have a helper function to aid in the construction of state machines where every possible transition is allowed (#26). However, this has problematic behaviour with large sets, e.g. Int or Integer.

Instead of having a single Topology type, we could have a GADT or typeclass with the following constructions:

• strict topology, which only allows the specified transitions
• open topology, which allows the specidied transitions ∪ identity transitions
• full topology, which allows every possible transition