code

ScalaCollider – saving presets with json

Sometimes it is useful to save presets when working with ScalaCollider. In Supercollider this is usually done with

writeArchive

and

readArchive

, which can be called on any object that does not contain open functions. After review several possibilities to do the same in scala, I found that the easiest is to use lift-json for JSON parsing and generation. JSON is a human readable format, which is quite convenient.

The easiest way to save a preset would be using case classes to hold the data, since lift-json can automatically serialize and deserialize them:

import java.io.{FileWriter}
import net.liftweb.json._
import net.liftweb.json.Serialization.{write,read}
import scala.io.Source._

object TestJsonSerialization {

  def main(args: Array[String]) {
    implicit val formats = DefaultFormats

    case class Person(name: String, address: Option[String], num:List[Int])
    case class Container(persons:List[Person])
    val people = Container(List(Person("joe", None, List(1,2,3,4)),
        Person("jack", Some("NY grand central"), List(5,6,7,8))))

    //write values to disk
    val fw = new FileWriter("test.txt")
    fw.write(write(people))
    fw.close()

    //get values back
    val jsonString = fromFile("test.txt").mkString
    println(pretty(render(parse(jsonString))))
    println(read[Container](jsonString))
  }

}

To compile the example with sbt use this project file:

import sbt._

class JSONProj(info: ProjectInfo) extends DefaultProject(info)
{
  val json = "net.liftweb" %% "lift-json" % "2.3"
}

Tags | JSON, Presets, scala, ScalaCollider

Scala pattern matching and variables

Today I was debugging some scala code for more than one hour. Turns out that if you use a variable in the pattern you are matching you need to put it in back ticks:

val thing = 3
4 match {
    case thing => println("bingo")
}

This code will match because thing will just became a new variable that is a container for whatever values are being matched.

val thing = 3
4 match {
    case `thing` => println("bingo")
    case _ => println("no match")
}

This code on the other hand will not match, because the variable thing is used, whose content is 3.

Tags | pattern matching, scala

scala compiled to LLVM and Scala.react

Today found a paper submitted at scala days 2011 on “Compiling Scala to LLVM” . That would probably give native speed to scala programs.  I will keep following the development of this.

Also interesting is the paper on “Scala.react: Embedded Reactive Programming in Scala” , also from scala days 2011.