2011 June

lift-json serialization pretty printing

The built-in serialization of lift-json prints a string with no newlines. I prefer to have a nicely printed string so that I can edit the file if I want. For this end I created a new function

writePretty

:

object JsonPimps {

  def writePretty[A <: AnyRef](a: A)(implicit formats: Formats): String =
    (writePretty(a, new StringWriter)(formats)).toString

  def writePretty[A <: AnyRef, W <: Writer](a: A, out: W)(implicit formats: Formats): W =
    Printer.pretty(render(Extraction.decompose(a)(formats)), out)
}

scala – iterate through elements of collection with their indexes

I finally discovered a nice syntax for iterating through a collection with the indices of each element provided:

List(9,9,9,9,9,9).zipWithIndex

res0: List[(Int, Int)] = List((9,0), (9,1), (9,2), (9,3), (9,4), (9,5))

Intellij – git, visual interactive rebasing, local history and SuperCollider

Wow, I’ve just discovered that the git integration in Intellij IDEA is quite advanced. It even does visual interactive rebasing, something which I couldn’t find in any of the shiny looking (and non-free) osx git visual apps.

It also automatically saves your files on every change and kees a private list of changes for the last couple of minutes/hours, which is basically a capable undo system for programmers.

Finally, today I’ve discovered that Intellij is actually a capable editor for SuperCollider classes. I use it to edit classes, but still rely on the SuperCollider app to run the actual code. I’ve made a basic xml file for supercollider syntax support.

I get for free the nice font rendering of plain text, all the git + local history functionality, tabbed editing, and folder layout with all my files. Also, it automatically strips whitespace, and I can position the cursor anywhere in the file and start typing

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.

Bwana – Graphical man pages in osx

I’ve been using Bwana to show me man pages in safari. Reading man pages in terminal is just ridiculous in 2011…

I use a little script to open the manpage from terminal:

open man:$1

I have saved it to

/usr/local/bin/mman

so I only have to do

mman ln

to get the man page for ln.

DiffMerge

git config --global diff.tool diffmerge
git config --global difftool.diffmerge.cmd "diffmerge "$LOCAL" "$REMOTE""

git config --global merge.tool diffmerge
git config --global mergetool.diffmerge.cmd "diffmerge --merge --result="$MERGED"
  "$LOCAL" "$BASE" "$REMOTE""
git config --global mergetool.diffmerge.trustexitcode false

git mergetool -t diffmerge

git difftool -t diffmerge master~1 myfile.sc