[racket] Documenting a financial model in Racket?

Hi,

At work I've inherited a financial application whose model that is too
complicated to be documented.

It has got me really curious how I might use Racket to document,
understand, and implement the model so that we can really flesh out
how it works. It would be useful purely from that regard, and also if
we ever migrated to a different technology (than Java).

What approaches, techniques, or features of Racket do you think might
be interesting?

My list: Typed Racket, in-code documentation, Rackunit,
purely-functional or perhaps classes and interfaces, not sure what
would be easier for people to read.

Best wishes,

Grant

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