What is the best way to learn Haskell for “real world use" (in 2019)?

https://typeclasses.com/phrasebook (especially the later lessons) has some nice little tutorials / tips and tricks showing off libraries you'd want to use in production for various tasks, very practical. (I haven't tried their for-pay courses, so can't comment on that.)

https://tech.fpcomplete.com/haskell/library/rio is a tutorial for an alternative prelude, perhaps a bit opinionated, but it shows a common "production" architecture.

> and not on how to build a production application (e.g. web service).

Yesod is the web framework I use in Haskell:

https://www.yesodweb.com/page/quickstart

https://www.yesodweb.com/book

For the database library, I prefer to use Esqueleto over Persistent, though:

https://hackage.haskell.org/package/esqueleto-2.4.3/docs/Dat...

In general, you'll want to use `stack` and Stackage[1] to manage your projects and package dependencies. Hackage[2] has the latest package submissions. Because they're simply the latest, they might be incompatible with one another. Stackage groups the compatible versions of all packages in Hackage into snapshots. `stack`, besides helping manage your dependencies, also has package templates for how a new project's files should be layed out.

[1] https://www.stackage.org/

[2] https://hackage.haskell.org/

Build a simple web service using Scotty or Spock.

http://hackage.haskell.org/package/scotty

https://github.com/scotty-web/scotty/wiki/Scotty-Tutorials-&...

The best way is to try and build a web app and learn along the way. Here's the stack I use for all my Haskell web apps:

- Stack to manage the project and dependencies.

- WAI and Warp to construct your own bare bones web app (see https://broch.io/posts/build-your-own-wai-framework/). I don't like frameworks like Yesod or Spock because I like to keep it simple.

- blaze-html (https://hackage.haskell.org/package/blaze-html) for constructing HTML.

- selda (https://selda.link) for PostgreSQL/SQLite interface (it might be too much for beginners, but there's other modules like postgres-simple).

- wai-extra for form/file upload parsing, gzip, and other basic middleware.

- wai-middleware-static for serving static files

- aeson for JSON encoding/decoding

This stack is what I use for building webapps with Haskell. If you're building JSON REST APIs you might want to look into Servant. I haven't used it personally but I hear good things.

I strongly recommend learning the basics of Functors, Applicatives, and Monads before venturing into building applications: See http://adit.io/posts/2013-04-17-functors,_applicatives,_and_... and http://adit.io/posts/2013-06-10-three-useful-monads.html If you know how Functors, Applicatives, and Monads work then you can understand almost everything about Haskell.

Good luck! Feel free to email me if you have questions.

Just to note, Haskell is not that pretty when used for "real world" tasks.