[BiteCode_dev]

Alright, so you get numbers from a json file in a ftp servers, you use scipy.newton to perform root finding on it, but needs the number of steps to be outputted as well (which newton() doesn't return), and you will save the result in a postgres table.

All this should be send to a task queue, triggered by a call to your REST API.

Good luck with purity.

[Leftium]

"Railway Oriented Programming"[1] is a (functional) technique to achieve purity despite steps that could result in error states. The error states are hidden/pushed to the very edges/end of your code. So you can focus on the "happy state" for the main business logic:

> Many examples in functional programming assume that you are always on the “happy path”. But to create a robust real world application you must deal with validation, logging, network and service errors, and other annoyances.

> So, how do you handle all this in a clean functional way?

> This talk will provide a brief introduction to this topic, using a fun and easy-to-understand railway analogy.

Functional programming keywords/shorthands: option/either/monads

[1]: https://fsharpforfunandprofit.com/rop/

[nordsieck]

> Good luck with purity.

Most of your counter example needs integration tests to test properly anyhow - not really a good point.

If you can give up encapsulation (which IMO isn't actually that useful in practice) and in return, your program becomes 95% functional, that seems like a really good tradeoff.

[nemetroid]

1. code that listens to a REST API and puts a request on a task queue

2. code that listens to the task queue for new jobs

3. code that fetches a file from the FTP server

4. code that converts the JSON file to a format appropriate for the root finding

5. code that performs the root finding

6. code that converts the result of (3) to a format appropriate for insertion into a table

7. code that inserts the result into a Postgres table

Steps 4, 5 and 6 seem easy enough to implement in a pure fashion.

[Izkata]

Yeah, just reading their description I was like "the middle part seems easily done as its own thing".

"Functional Core, Imperative Shell" was just posted too, this is the perfect example of where that structure works: https://news.ycombinator.com/item?id=34860164

[pancrufty]

You’re describing a bad API to begin with. Those are too many steps to test at once too.