> In order to write that you have to pin a reference to the state Forgive my ignorance, but why is that the case? Isn't `state` being passed into the loop? Mu

> In order to write that you have to pin a reference to the state Forgive my ignorance, but why is that the case? Isn't `state` being passed into the loop? Mutability is orthogonal to the question of where one defines a unit of behavior. Maybe an immutable object is not possible to achieve in F#, but one could certainly imagine the concept of an immutable type with methods. My question is more about the modes of organization: Large unions vs discrete modules and how they affect how one's ability to change a program over time. If you say that the architecture was chosen out of a purest sense of FP, then fair enough. I can understand why someone would go that route. Just had to know.