Http4s VS fp-ts

http4s is a Typelevel project, and therefore falls into the "program in Scala as if it were Haskell" category. Many people find this off-putting, but honestly, I think with the resources listed above, this is the option at the best intersection of "mature" and "well-documented" available in Scala. The reason it's off-putting to many people is that Haskell-style pure FP isn't mainstream, so it isn't so much a matter of learning a new technology as it is a matter of learning a new paradigm, which necessarily means surfacing and unlearning things you already know, and perhaps confronting the uncomfortable feeling that things you thought were "fundamental," "have to be that way," aren't, and don't. I personally found this process liberating. But not everyone does.

If you want a mature REST API library, I recommend http4s. Be aware, though, that it’s based on purely-functional programming with Cats, cats-effect, and fs2, so if you’re not familiar with them or aren’t prepared to commit to the paradigm, the learning curve may be daunting, seem pointless, or both.

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.

Most important/known: * https://http4s.org/ - an HTTP client/server * https://github.com/typelevel/fs2 - streaming * https://github.com/tpolecat/doobie - JDBC

Scala devs are too busy wondering about free monads and F[Request[F] => Response[F]]. I am very pleased by http4s, Doobie, ScalaJS, and the whole ecosystem, really: https://http4s.org

In reality, your performance issues will not be http4s, but something else. That being said, there are improvements that http4s can and is making, and I'm quite excited about the future 1.0 release, which has some important and fundamental performance improvements already, like a a 125% performance improvement on the plaintext benchmark from https://github.com/http4s/http4s/pull/6091 - and finally, yes, akka-http does have very good performance, but you can also get good performance out of http4s.

http4s for REST services.

This is a long list of misunderstandings I don’t have the patience to unpack. Instead, let me refer you to the links in my top comment in the thread, then suggest you learn at least http4s, a purely-functional web service library that’s been used in production for a decade or so now.

The most popular nowadays are - I guess - akka-http and http4s. You can also use Play if you don't want to start from scratch but prefer a framework-based approach.

There are functional frameworks: https://http4s.org/

I think it’s great that functional programming is making its way into traditional imperative languages - even JavaScript (I recently came across https://gcanti.github.io/fp-ts/ as a pretty extreme example)

Elixir/Erlang has function-level pattern matching, which I really like. I’ve yet to see it anywhere else, though my understanding is it came from Prolog.

While I certainly agree, I've found that this is often an indication of too-complex an architecture, and a fundamental re-think being necessary. I've had projects that depend on [fp-ts], which end up incredibly generic-heavy, but still make it entirely through a typecheck(not build- typescript's just worse at that than other tools like esbuild) in seconds-at-worse.

Obviously depends on your organization/project/application, but I do like these things as complexity-smells.

[fp-ts]: https://gcanti.github.io/fp-ts/

Unlike more comprehensive functional libraries like fp-ts, each module can be imported and resolved separately. If you just need options, simply add the option module and you're good to go.

While it's quite abstract, I believe it may be useful to those of you who is interested to learn more about functional programming [in Typescript] and also get more intuition on diverse programming ideas. I use fp-ts as a functional programming library there.

The library for TypeScript that this is influenced by is here:

https://github.com/gcanti/fp-ts

Interesting how both languages with this library converge to a similar syntax, due to heavy use of functions.

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.

fp-ts, a library that caters to functional programming in TypeScript, comes with some micro-abstractions that already solve a few of our needs.

Also, don't underestimate how powerful TypeScript can be in capable hands (namely Giulio Canti's). Check out fp-ts, for instance.

You are able to type it using function overloads, an example can be found here - link, line 236.

looks like more ergonomic/focused version of fp-ts[1]

[1] https://gcanti.github.io/fp-ts/