I've done a lot of Haskell, and my approach tends to be a mix of the two. There's a natural split: • types let me play with the architecture and interfaces top

I've done a lot of Haskell, and my approach tends to be a mix of the two. There's a natural split: • types let me play with the architecture and interfaces top-down • the REPL lets me write more complex logic bottom-up Usually there are a few "hotspots" in the codebase that require a lot of logic and are easier to develop bottom-up; the rest of the codebase is focused more on organization, domain modeling and information flow, where top-down design works really well. In actual practice I expect my mode tends to vary even more than that, but this division seems like a good approximation of how I think about it.