scalaz

Introduction#

Scalaz is a Scala library for functional programming.

It provides purely functional data structures to complement those from the Scala standard library. It defines a set of foundational type classes (e.g. Functor,Monad) and corresponding instances for a large number of data structures.

ApplyUsage

import scalaz._
import Scalaz._

scala> Apply[Option].apply2(some(1), some(2))((a, b) => a + b)
res0: Option[Int] = Some(3)

scala> val intToString: Int => String = _.toString

scala> Apply[Option].ap(1.some)(some(intToString))
res1: Option[String] = Some(1)

scala> Apply[Option].ap(none)(some(intToString))
res2: Option[String] = None

scala> val double: Int => Int = _ * 2

scala> Apply[List].ap(List(1, 2, 3))(List(double))
res3: List[Int] = List(2, 4, 6)

scala> :kind Apply
scalaz.Apply's kind is X[F[A]]

FunctorUsage

import scalaz._
import Scalaz._
scala> val len: String => Int = _.length
len: String => Int = $$Lambda$1164/969820333@7e758f40

scala> Functor[Option].map(Some("foo"))(len)
res0: Option[Int] = Some(3)

scala> Functor[Option].map(None)(len)
res1: Option[Int] = None

scala> Functor[List].map(List("qwer", "adsfg"))(len)
res2: List[Int] = List(4, 5)

scala> :kind Functor
scalaz.Functor's kind is X[F[A]]

ArrowUsage

import scalaz._
import Scalaz._
scala> val plus1 = (_: Int) + 1
plus1: Int => Int = $$Lambda$1167/1113119649@6a6bfd97

scala> val plus2 = (_: Int) + 2
plus2: Int => Int = $$Lambda$1168/924329548@6bbe050f

scala> val rev = (_: String).reverse
rev: String => String = $$Lambda$1227/1278001332@72685b74

scala> plus1.first apply (1, "abc")
res0: (Int, String) = (2,abc)

scala> plus1.second apply ("abc", 2)
res1: (String, Int) = (abc,3)

scala> rev.second apply (1, "abc")
res2: (Int, String) = (1,cba)

scala> plus1 *** rev apply(7, "abc")
res3: (Int, String) = (8,cba)

scala> plus1 &&& plus2 apply 7
res4: (Int, Int) = (8,9)

scala> plus1.product apply (1, 2)
res5: (Int, Int) = (2,3)

scala> :kind Arrow
scalaz.Arrow's kind is X[F[A1,A2]]