learning Scalaz: day 1


Hey there. There's an updated html5 book version, if you want.

How many programming languages have been called Lisp in sheep's clothing? Java brought in GC to familiar C++ like grammar. Although there have been other languages with GC, in 1996 it felt like a big deal because it promised to become a viable alternative to C++. Eventually, people got used to not having to manage memory by hand. JavaScript and Ruby both have been called Lisp in sheep's clothing for their first-class functions and block syntax. The homoiconic nature of S-expression still makes Lisp-like languages interesting as it fits well to macros.

Recently languages are borrowing concepts from newer breed of functional languages. Type inference and pattern matching I am guessing goes back to ML. Eventually people will come to expect these features too. Given that Lisp came out in 1958 and ML in 1973, it seems to take decades for good ideas to catch on. For those cold decades, these languages were probably considered heretical or worse "not serious."

Looking back to our Scala community, it pains me to see people jeering at Scalaz. I'm not saying it's going to be the next big thing. I don't even know about it yet. But one thing for sure is that guys using it are serious about solving their problems. Or just as pedantic as the rest of the Scala community using pattern matching. Given that Haskell came out in 1990, the witch hunt may last a while, but I am going to keep an open mind.

tetrix in Scala: day 12

Yesterday we've created two stage actors so the agent can play against the player. To make things more interesting, attacking was implemented which sends junk blocks to the opponent.

unfair advantage

tetrix in Scala: day 11

Yesterday we've written a test harness to automate scripted games to tune various components of the heuristic function. The overall performance improved from 7 +/- 2 lines to 34 +/- 18, almost 5x improvement.

HAL moment

tetrix in Scala: day 10

Yesterday we expanded the search tree of the tetrix-solving agent into second piece. Although the quality of the game it is able to play has improved, there are some more room for tweaking.


tetrix in Scala: day 9

Yesterday we got the tetrix-solving agent to play a better game by fixing the heuristic function and evaluating 36 possible positions of the current piece.

stop watch

Let's start by creating a function to measure the time it takes to run a segment of code:

  private[this] def stopWatch[A](name: String)(arg: => A): A = {
    val t0 = System.currentTimeMillis
    val retval: A = arg
    val t1 = System.currentTimeMillis
    println(name + " took " + (t1 - t0).toString + " ms")

tetrix in Scala: day 8

Yesterday we hooked up our tetrix-solving agent to an actor to take control of the game. Thus far the way it handled the game looked neither rational nor intelligent. After seeing many of the moves evaluated to 0.0 score including the heuristic penalties, I had two sneaking suspicions.

tetrix in Scala: day 7

Yesterday we started on a new challange of building tetrix-solving AI. Russell and Norvig give insight into how a rational agent can be structured using a state machine , a utility function, and a tree searching algorithm. We have the first two, and a failing test:

[info] Solver should
[info] + pick MoveLeft for s1
[error] x pick Drop for s3
[error]    'MoveLeft' is not equal to 'Drop' (AgentSpec.scala:13)

tetrix in Scala: day 6

Yesterday we improved the concurrent access of the game state by introducing a second actor. Now that we have a powerful tool to manage concurrency, we can venture out to somewhere new. Like taking over the mankind. One tetrix player at a time.

Russell and Norvig

tetrix in Scala: day 5

Yesterday we put in an Akka actor to manage concurrent access to the game state. Let's look at the abstract UI again:

package com.eed3si9n.tetrix
class AbstractUI {
  // skipping imports...
  implicit val timeout = Timeout(1 second)
  private[this] val initialState = Stage.newState(Block((0, 0), TKind) :: Nil,
    randomStream(new util.Random))
  private[this] val system = ActorSystem("TetrixSystem")
  private[this] val playerActor = system.actorOf(Props(new StageActor(

tetrix in Scala: day 4

In the last few days, we implemented tetrix from the ground up. In the beginning I mentioned that I use this game to explore new ways of thinking. Since I had already implemented tetrix once in Scala, Scala alone really isn't anything new for me. The actual topic I wanted to think about using tetrix is the handling of concurrency.

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