[mixedCase]

With a good type system, instead of writing algorithms first you would write data structures that convey the ideas behind the software's intent clearly. Then you start writing the algorithms that manipulate these data structures.

If what you're trying to do is viable, then you'll be able to express it in the domain model.

[sk5t]

Yes! I've found it quite effective to start new problems with some (mostly composition-based) types as a means of jotting down the core inputs and outputs, then work out towards the edges in both directions with deserializers/readers/parsers in one direction, and repositories and work-doing algorithms in the other direction. A little dependency injection to wire the pieces together in complex systems and you're in business.

[jmull]

I usually start design with a domain model, whatever the type system I'll be working with.

(Just pointing out you can go this route regardless of your type system.)