Railway-oriented programming

The elided punchline is that this entire essay is "just the `Either` monad". If you can forgive the snark there, the point to take home is that this entire pattern of programming can be nicely summarized through some very high-order topics like Monads. That's one "why" for "why should I learn what 'monad' means". A very similar essay could be written for non-deterministic programming ("it's 'just' the List or Logic monad"), for backtracking parser combinators ("they're 'just' the State +…

I really think that's an useful tutorial for all languages with exceptions ( that's an exceptional event ) and normal control flow ( application error, validation, retry ). Like that code become really simple, but more expressive than returning an int error code each function. A function can return an error with messages or message+data or message+retrycount etc. With F# (can be done in other languages obv) it's really easy to have different success/failure return types ( amazing type inference…