Simulacrum VS Ammonite-Ops

The Cats ecosystem offers mature named abstractions providing algebraic laws virtually identical to those offered by Haskell and PureScript and that have stood the test of time, at the cost of relying on a "design pattern" approach to implementation you have to squint a bit to see ("typeclasses" based on higher-kinded types and implicit arguments) and that sometimes doesn't play nicely with Scala's colored local type inference. The selling point of this, coupled with parametricity ("tagless-final style"), is the ability to reason algebraically about your code.

The indent based syntax is only available in Scala 3, you have to download a matching ammonite version from https://github.com/com-lihaoyi/Ammonite/releases

That's funny, because this is what I really like about Scala; how quick and easy it is to get a project started.

> sbt new scala/scala3.g8

will just create an empty project. If you don't even want to bother with a project, use use scala-cli or ammonite (http://ammonite.io/) to just start banging out code.

Even the upgrading of a project from Scala2 to Scala3 is a breeze, thanks to very good backwards compatibility of new library releases.

Ammonite is a very good REPL for Scala. You can invoke it with amm and type expressions into it, or load a Scala “script file” whose name ends with .sc into it, or many other things. It’s documented at https://ammonite.io. 2. sbt is the dominant build tool for Scala projects. As others have commented, when you open a folder in Visual Studio Code and try to make Metals “aware of it,” it expects to find a “Scala project” in the folder. A “Scala project” isn’t just Scala source code. See https://www.scala-sbt.org for details. 3. Also be aware that Metals supports worksheets, so you can easily experiment with code in your project interactively, too.

Scripting API is quite limited, so the third option. - reuse the ammonite scripts https://github.com/com-lihaoyi/Ammonite or look how this is implemented (using internal compiler API),

Your exposure to Functional Programming with Haskell and Clojure suggest you will certainly pick up Scala quickly. With ZIO and cats, you can write robust software quickly. Consider the excellent Coursera Scala course. Get "the Red Book" https://www.manning.com/books/functional-programming-in-scala, and most important, play. Experiment to see how things work. Get https://ammonite.io/

Here's an example of a smaller project that added telemetry without suffering a fork:

https://github.com/com-lihaoyi/Ammonite/issues/607

Or ammonite - I've ran Gatling performance test from a simple script based on this gist it fetches all the dependencies, compiles and runs the test, producing nice html report..

Scala with the Typelevel ecosystem. Stay on the jVM, but have a much more pleasant and robust experience, including a great REPL.