I think there's still a category theoretic expression of this, but it's not necessarily easy to capture in language type systems.

The notion of `f` producing a lazy sequence of values, `g` consuming them, and possibly that construct getting built up into some closed set of structures - (e.g. sequences, or trees, or if you like dags).

I've only read a smattering of Pi theory, but if I remember correctly it concerns itself more with the behaviour of `f` and `g`, and more generally bridging between local behavioural descriptions of components like `f` and `g` and the global behaviour of a heterogeneous system that is composed of some arbitrary graph of those sending messages to each other.

I'm getting a bit beyond my depth here, but it feels like Pi theory leans more towards operational semantics for reasoning about asynchronicity and something like category theory / monads / arrows and related concepts lean more towards reasoning about combinatorial algebras of computational models.