cats VS cats-effect

A functional programming library: https://typelevel.org/cats/

Learn something that pays the bill first - nowadays it's Golang/Rust react/typescript. Then you can try some pure fp libs like fp-ts and fp-core.rs, and look through existing scala cats docs. If you'll feel bad about it - that's totally fine and expectable, fp takes a paradigm shift and not that many dev able to shift their brains way of thought due to basic psychological rigidity) (inability to change habits and to modify concepts/attitudes once developed). And that's purely a staffing and management issue - folks hired randoms out of the blue, and called 'em a team.

I'm sorry, but have you ever done functional programming for a real company, like in a functional programming language like Haskell, Scala, or F#? Have you ever used Scala cats or scalaz? Have you ever learned category theory and how to apply its abstractions in software? Listen u/judethedude2106 this person hasn't gone as far down the functional programming rabbit hole as I have. Beyond learning the basics like the difference between pure and impure functions, what are closures, what higher order functions are and the most common ones like .map, .filter, and .flatmap, the immutable collections like immutable linked lists and trees, and what a Monad is and common monads like those used for futures/promises, async programming, and Option (Some or None, which is used instead of null checking), the more advanced functional programming stuff like category theory based abstractions are totally useless for real jobs and is just a giant time suck. Don't waste years on functional programming, spend at most a few months on it and no more.

As a former functional programmer in Scala, please do not go deep into the Category Theory programming. Scala has libraries like this one called "Cats", a cute shortened name for "Category Theory", but code that makes heavy use of these constructs is not understandable to other programmers. Other than using Monads as a design pattern for things like Options (which can be "Some" or "None"), Futures or Promises (which is used for asynchronous programming), and a few other things, please do not make heavy use of category theory constructs in real programming projects that will have other developers working on them. It is a rabbit hole that may be fun but is not super practical. Sure, write pure functions without side effects, but do not use the words "Bimonad", "Invariant Monoidal", and "Semigroup" in your code. The most common, practical application/use of functional programming is basic things like closures, .map, .filter, maybe chaining maps with like a .flatmap or whatever your programming language uses instead of chain or flatmap, and SQL that uses keywords like WHERE which can be represented in code by using a call to .filter. Like the place where these constructs are used most is in data processing like with SQL, ETL (Extract Transform, Load) jobs, Java's MapReduce on Hadoop, Scala's Apache Spark, and other data processing type things. Haskell is not a popular programming language in real world projects for a number of reasons and one of them is the heavy and sometimes impractical use of Category Theory.

At a previous job of mine we actually had an entirely pure Scala ecosystem using cats which instead uses typeclasses, referential transparency, and other FP concepts as the foundations for how to code. So a lot of flexibility to the language.

Thanks! It's used heavily here

I did work in Scala for a few years. We employed Cats[1], and even a bit of Matryoshka[2] though most of the work I do today is in Python.

Nowadays I think about computational requirements in terms of relations among behavioral dependencies. Like, "I want to perform operation O on input A and return a B. To do this, I'll need a way to a -> b and a way to b -> b -> b." I often pass these behavioral dependencies in as arguments and it tends to make the inner core of my programs pretty abstract and built up as layers of specificity.

Zooming out nearly all the way, it makes me feel tethered in a qualitatively unique way to certain deep truths of the universe. In a Platonic sense, invoking certain ideas like a monad make me feel like I'm approaching the divine or at least one instantiation of a timeless universal that operates outside of material existence.

I'd imagine some mathematicians might see the universe in a similar way - one where immortal relations between ontological forms exist beyond time and space and at the same time can be threaded through the material world by intellectual observation and when those two meet a beautiful collision occurs.

1. https://typelevel.org/cats/

2. https://github.com/precog/matryoshka

Our second type class example attempted to illustrate one last perk: type safety at compile time. It did so with a simplified example of the cats core library for type safety equality comparison between objects. If you're not familiar with cats, go ahead and give it go.

3) Finally, Scala 3 + cats is a great middle ground. It's a great language to teach and learn FP, even if you learn by yourself, without support from other people. There are lots of materials and even if you get stuck with a concept, you can still implement it using what you knew before.

Those benchmarks are using a snapshot version of cats-effect. I don't know where that one comes from, but previously they were using a snapshot from https://github.com/typelevel/cats-effect/pull/3332 which had some issues (3.5-6581dc4, 70% performance degradation), which have since been resolved (see that PR for more info and comparative benchmarks).

Recently, CE3 has had similar issues reported across multiple repositories, almost an epidemic of reports!

The one advantage Rust has over Scala is that it detects data races at compile time, and that's a big time saver if you use low level thread synchronization. However, if you write pure FP code with ZIO or Cats Effect that's basically a non-issue anyway.

See also cats-effect and fs2. cats-effect gives you your IO Monad (and IOApp to run it with on supported platforms). fs2 is the ecosystem’s streaming library, which is much more pervasive in functional Scala than in Haskell. For example, http4s and Doobie are both based on fs2.

On the contrary, switching to the functional mindset, with something like Typelevel Scala3 and respective cats and cats-effect fs2 frameworks, helps to rethink a lot of designs and development approaches.

I think "better Haskell on JVM" (in contrast to "worse Haskell") is a good identity for Scala to have. (Please note that this is an intentional hyperbole.)

Of course, there are areas where Haskell is stronger than Scala (hint: modularity, crucial for good Software Engineering, is not one of them). And Scala has its own way of doing things, so just imitating Haskell won't work well.

Examples of this "better Haskell" are https://typelevel.org/cats-effect/ and https://zio.dev/ .

All together, Scala may be a better choice for you if you want to do Pure Functional Programming. And is definitely less risky (runs on JVM, Java libraries interop, IntelliJ, easy debugging, etc...).

None of the other languages you mentioned are viable in this sense (if also you want a powerful type system, which rules out Clojure).

I agree that Rust's identity is pretty clear: a modern language for use cases where only C or C++ could have been used before.

I would use Scala. I like FP and Scala comes with some awesome libraries for concurrent/async programming like Cats Effect or ZIO. Good choice for creating modern style micro-services to be run in the cloud (or even macro-services, Scala has a powerful module system, so it's made to handle large codebases).

https://typelevel.org/cats-effect/

https://zio.dev/

The language, the community and customs are great. You don't have to worry about nulls, things are immutable by default, domain modelling with ADTs and patter matching is pure joy.

The tooling available is from good to great and Scala is big enough that there are good libraries for typical if not vast majority of stuff and Java libs as a reliable fallback.

The author is the creator of Monix and implemented the first version of cats-effect. He knows what he is doing.

You want Kernmantle, which quite honestly shouldn't be hard to implement around Cats and cats-effect. In particular, although Kernmantle doesn't require the use of the Arrow typeclass, there happen to be Arrow (actually ArrowChoice) instances for both Function1 from the standard library and Kleisli from Cats itself, given a Monad instance for the Kleilsi's F[_] type parameter. In other words, we should be able to port Kernmantle from Haskell to Scala (with the Typelevel ecosystem) and instantly be able to use pretty much anything else from the Typelevel ecosystem, or wrapped with it, in our workflow graphs. Pure functions, monadic functions, applicative functions, GADTs with hand-written interpreters, any of it. I think this would be eminently worth doing.