n4to4 / harmony

Scalaz and Cats compatibility

Harmony

A Cats and Scalaz compatibility library.

Tired of writing separate code for Cats and Scalaz? All that preprocessor noise and those extra packages are too much work! Just pick between Scalaz and Cats. If your clients don't like your choice, they can use one import from this library to become happy.

We can all live together!

Usage

SBT dependency

cats version	scalaz version	harmony version	dependency
0.8.1	7.2.*	1.0	"me.jeffshaw" %% "harmony_cats0.8.1_scalaz7.2" % "1.0"
0.9.0	7.2.*	1.0	"me.jeffshaw" %% "harmony_cats0.9.0_scalaz7.2" % "1.0"

The naming scheme will change if Cats or Scalaz change their binary compatibility guarantees. Cats has no such guarantee.

Imports

Harmony releases sharing an artifact name and major version should be binary compatible.

domain	codomain	type class	data types	both
Cats	Scalaz	import harmony.toscalaz.TypeClasses._	import harmony.tocats.Data._	import harmony.ToScalaz._
Scalaz	Cats	import harmony.tocats.TypeClasses._	import harmony.tocats.Data._	import harmony.ToCats._

Or, if you just want everyone to get along,

import harmony.Everyone._

Examples

Want a cats.Functor for scalaz.IList?

import harmony.tocats.typeclass.FunctorConverter._

cats.Functor[scalaz.IList]

Want a to use a scalaz.Writer in a cats.data.Writer?

import cats.instances.int._
import harmony.tocats.data.WriterTConverter._

val tell3 = scalaz.WriterT.tell(3)

val w: cats.data.WriterT[cats.Id, Int, Unit] =
  for {
    _ <- cats.data.Writer.tell(2)
    _ <- tell3
  } yield ()

w.run // yields (5, ())

Provided conversions

Please see the Google doc.

Something missing?

Please fork this repo, add the relevant conversions to the relevant files, and do a pull request.

Or you can open an issue describing the conversions you need and someone might do it for you.

Tests

Harmony could use many more tests. As the library gains popularity I will add more.