[tomrod]

I wish I knew enough compsci to know why functional programming is useful. I read about half the book, and while interesting from a learning perspective I don't know where I can apply it.

Context: self-taught programmer in the data science/statistical modeling world.

[steve_adams_86]

Since I've started applying FP (I'm not very strict about it) I've been finding ways to reuse code more which lets me reduce my test footprint and increase the reliability of my code. I've also found it's easier to isolate my business logic without scoping it too strictly to an object or implementation, allowing me to think largely in coding to interfaces or contacts. This is totally doable with strict OO, but honestly I'm pretty lousy at that in practice. So FP has helped me with that too.

I lean towards organizing my applications into very dumb objects which are supported by FP-style business logic. At a glance you can infer what's going on quite easily due to the idiomatic use of the objects, but the object orientation mostly ends there. My business logic is organized into isolated modules that are as pure as I can manage without being a nut about it. The objects recruit or are operated on by that logic, so their implementation is very light and clean as a result. Like I mentioned, tests for this kind of code are really nice. They tend to be concise.

It's not perfect, but I feel like it's a way FP has greatly improved my code and what I deliver to my team in general. It's an attempt to merge the benefits of two paradigms, I suppose.

[charlieflowers]

You don't really need compsci to understand that.

A pure function is more of a declaration of truth than a list of steps. When your whole application is made up of declarations of truth, it is simpler to reason about and rearrange.

It's simply the fact that the function depends on nothing but its inputs (but includes all the surprising ramifications of that).