atom-scala

Clojure-style atoms for Scala

Atoms manage shared, synchronous, independent state. Intended to hold immutable data-structures.

• Thread safe
• Uses uses a CAS (compare and swap) for safe updates
• Fast
• Covers 90% of your state managements needs (based my empirical evidence)

Artifacts

Add the following lines in your build.sbt;

resolvers += "Sonatype snapshots" at "http://oss.sonatype.org/content/repositories/snapshots/"

libraryDependencies += "io.github.martintrojer" % "atom-scala_2.10" % "0.1-SNAPSHOT"

Usage

The main function swap takes a side-effect free function that gets called with the old state and produces the new state. Please be aware, this function can be called multiple times!

The reset function simply overwrites the old value.

scala> import Atom._
import Atom._

scala> val a = Atom(1)
a: Atom.Atom[Int] = 1

scala> a swap { _ + 1 }
res0: Int = 2

scala> a.get
res1: Int = 2

scala> a.reset(42)

scala> a.get
res2: Int = 42

Supports Monadic Usage

// map
scala> Atom(42) map { _ + 1 }
res3: Atom.Atom[Int] = 43

scala> for ( v <- Atom(Set('a)) ) yield v + 'b
res4: Atom.Atom[scala.collection.immutable.Set[Symbol]] = Set('a, 'b)

// flatMap
val a1 = Atom(Map('a -> 1))
val a2 = Atom(Map('b -> 2))
for {
  v1 <- a1
  v2 <- a2
} yield (v1 ++ v2)
res5: Atom.Atom[scala.collection.immutable.Map[Symbol,Int]] = Map('a -> 1, 'b -> 2)

// foreach
var res = 0
val a = Atom(42)
for ( v <- a ) {
  res = res + v
}
res: Int = 42

References

• Clojure Atoms
• Akka Agents (inspired by Clojure's Agents)

License

Copyright (C) 2013 Martin Trojer

Distributed under the Eclipse Public License.