[naasking]

> Let's say I want to stream logging data at a massive rate (~peak core-core bandwidth) to another core and perform complex queries and visualisations on it in sub-frame times. If I have the data structure for that, the rest is bookwork. If I have the type... what have I gained?

It depends on how you're using "type" vs how I'm using it.

If you mean the "publicly visible type", ie. the left hand side of "newtype Foo a = ...", my claim is weaker. Even so, the public interface for your type specifies the operations and implies their approximate time and space complexity (1), which points rather suggestively at the types of internal data structures that will be needed to satisfy these properties (2), which as you've said, is at least half the problem.

If by "type", the actual data type definitions needed to satisfy this interface, ie. the right hand side of "newtype Foo a = ...", which is what I originally meant, then you're already at (2) above, from which the conclusion follows almost trivially.

Hopefully that clarifies your follow up points.