Tapestry final coming soon !

On the tech side, it's a good time for me !

Soon after the release of Scala 2.7.2, it's Tapestry 5 time to reach an RC status (OK, I didn't blog about the RC1, some personal stuff were more important at this time).

Moreover, Tapestry 5 is gaining a kind of hype in Europe, or at least in France : the new official French weather site is coded with T5, and it's a big one (about 800,000 visitors in a day), and I just learn that Unedic[1], the French civil service for the unemployed, which a BIG civil service (as most of them in France ;), chose Tapestry 5 as there new default "ligth" web framework.

I'm quite happy of my choice for T5, almost 2 years ago :)

[1] sorry for the English readers, I didn't find an English description about Unedic :/

Windows refound if when you buy a computer

It's the first time I ever see that in the description of a new computer. It's saying : "ask a vendor if you don't want Windows Vista with your new computer, the refound is 50€". The computer was an Acer of about 500€, it was in a big electronic french brand, and that's reaaly cool.

Minds are evolving...

Scala 2.7.2 is out

Here we are, Scala 2.7.2 was released on november, the 10.
And it's a great news !

You may wonder why a minor release seems to be so important ?

C'm'on, it's a palindromic release number, it's so fantastic !

Well, more seriously, it's because this released is the one that will be cover by the coming book "Programming in Scala", and so, this release mark a kind of shift in the Scala language development : Until now, the language was evolving quite quickly, what was great in term of enhancement, but bring some recurring problems, and seems to frighten a lot "the enterprise developers" (or at least there bosses).

With this release, seconded by a great book, the Scala language reach a new level of maturity, and perhaps will gain more visibility outside the rather small (but growing !) circle of first time enthusiastic who use it today.

So, it's a great news for Scala users, and a great time to go and discover Scala !

ProjectEuler#42, aka Scala shines as a scripting language

I'm still playing with project Euler, and I'm going to love Scala more and more.
Yesterday, I solved the #42 problem, on which we need to parse a text file, and make some simple transformations and filtering on the results (it's why I choose this title, because it's generally the kind of things you expect to do in a scripting language, and well, I'm really
impressive, and I read this morning the post "Scala as a scripting language?", and I say "ho, it's exactly what I felt when I did pb#42 yesterday, let's blog on it, it's fashion :)

So, this problem is a simple Project Euler one (at least, there is no math on it), but just stop and think to what may look the Java's solution. Yes, you will have to deal with Files, input stream, and the like, filtering data, sorting things, and even if it's quite simple, it's always a little too heavy compared to what it may be.

So, there is the full solution in Scala, in a mixed imperative and functional style, as produced in the first sketch version (OK, I'm lying, in the first sketch, I didn't include comments and variables names looked more to 'lsv' and the like, these transformations are blog add-ons).

I'm sure there is a lot of optimizations available, but the important think is that Scala let you program as you think, whitout to much noise and boilerplate...

So let's go for the code:

package ex26_50
import scala.io.Source 
/*
Problem#42
The nth term of the sequence of triangle numbers 
is given by, tn = n(n+1);
so the first ten triangle numbers are: 
1, 3, 6, 10, 15, 21, 28, 36, 45, 55, ...

By converting each letter in a word to a number corresponding to its
alphabetical position and adding these values we form a word value.
For example, the word value for SKY is 19 + 11 + 25 = 55 = t10.

If the word value is a triangle number then we shall 
call the word a triangle word.

Using words.txt (right click and 'Save Link/Target As...'), 
a 16K text file containing nearly two-thousand common English 
words, how many are triangle words? 

*/

object Problem42 extends Application {

/*
 * iterate over all the lines of a file and
 * split each one on ',', remove surronding ",
 * and put the result in a list
 */
def parseWords(file:String): List[String] = {
   for {
     line <- Source.fromFile(file).getLines.toList
     s <- line.split(",")
     if(!s.isEmpty)
   } yield s.replaceAll("\"","") 
}  

/*
 * Simple mapping function that associate
 * each char to it's value (position in the alphabet, begin to 1)
 * and a word to the sum of its char value
 */
  def wordValue(s:String) : Int = { 
    var sum = 0 
    for(c <- s) {
      // iterate over the chars of the string
      val cval = c.toInt
      if(cval >= 64 && cval <= 90) {  
        // 64 = ascii val for 'A', 90 = ascii val for 'Z'
        sum = sum + cval - 64 
      } else {
        error("Unauthorized char: " + c.toString) 
      } 
    }
    sum
  }

/*
 * That's the definition of the list number on witch we will work:
 * - parse the file to a list of word
 * - transform each word to it's word value 
 * - sort the resulting, so that we can know the
 *      upper bound of our triangle value to caluculate            
 */

  val list_wordValues = 
    parseWords("src/words.txt").map(wordValue(_)).sort(_ > _)

//we also see that in Scala, Format syntax is actually usable
  println("Max value in %s words: %s (min: %s)".format(
      list_wordValues.size, 
      list_wordValues.head, 
      list_wordValues.reverse.head))

  /*
   * Given the upper bound,
   * generate the set of triangle number
   */
  val set_triangles = {
    var set = Set[Int]()
    var n = 1
    var i = 1
    while (n < max ) {
      n = (i * (i+1))/2
      i = i + 1
      set = set.+(n)
    }
    set
  }

  /*
   * That's all, we just have to filter the list of words to
   * only keep whose which are in the set of triangles value,
   * and take the size of the resulting list.
   */ 
  val nb = list_wordValues.filter( (i:Int) => 
             set_triangles.contains(i)).size

  println("Found %s triangles words !".format(nb))
}

I love scala :)

PS: It's the full working solution, appart from the leading "_", sorry for the formatting, it seems that blogger is not the most friendly for code formatting. If somebody has some hint on that subject, I will be glad to heard them (ok, perhaps I should have a look on the plugins)

EDIT: I found a way to highlight code thanks to SHJS. Thanks to the author for this plugin that wasn't to hard to make it work with blogger, and which the only Javascript highlighter that supports Scala :)