How does the Cats library in Scala relate to scalaz?

Question

How does the Cats library relate to scalaz? The Cats project mentions it is descended from scalaz.

Gainor

The cats Gitter channel would be a much better place for a question like this, but see for example this blog post for some context from the early days of the project (i.e. two months ago). – Hodgkin

Answer 1

I would like to keep this from getting too political*, but cats is for all intents and purposes scalaz. It has not reached full parity as of yet, but keep in mind it was only created a few months ago. The goal is for it to be a more pragmatic approach and more democratic when it comes to its evolution. So, naming of operators and classes is hopefully going to be a little more straightforward, as well as it has no qualms with using mutable data within a method if it means better performance. Last, they are HOPING to have better documentation....all of this means that it may end up becoming a replacement for scalaz with a better beginner's approach for those not embroiled in the math world. If you want a fuller answer, then maybe head over to their gitter board and Erik (non) could answer it himself :)

*The gist is that scalaz has some social baggage with it that causes a number of big names to shy away from using and/or contributing.

Sialagogue

There are significant technical differences, especially in terms of priorities. Cats has more of a focus on performance, on eliminating boilerplate through instance derivation and plugins like Simulacrum, etc. In general it's also likely to be less fundamentalist (or more open to compromise) on issues of purity, but it's too early to say much about how it'll end up differing from Scalaz in that respect. – Hodgkin

Agreed. I was trying to convey most of that, but I like the way you put it also :) – Sialagogue

Answer 2

just want to mention here that fairly recently scalaz became as well a namespace for a bunch of new, fp libraries, like testz, scalaz-zio, scalaz-metrics, scalaz-http, scalaz-analytics and more. And ScalaZ 8 is on the way!

Reynalda