Scala で XML を Parse する(添削希望)

Scala で XML を Parse してみたのですが、今ひとつカッコ悪いコードになってしまいました。
凄腕の Scala Hacker に添削して欲しい所です… orz

import scala.io.Source
import scala.xml.{Node, NodeSeq}
import scala.xml.parsing.XhtmlParser

object Test {
  def main(args:Array[String]) = {
    val source = Source.fromFile("/opt/local/share/scala-2.8/doc/scala-devel-docs/api/index.html")
    val xhtml = XhtmlParser(source)
    source.close

    val titles = List(
      "div" -> compareAttr("id", "tpl"),
      "ol"  -> compareAttr("class", "packages"),
      "li"  -> compareAttr("class", "pack"),
      "ol"  -> (compareAttr("class", "templates") orElse compareAttr("class", "packages"))
    ).foldLeft (
      xhtml \\ "div" filter(compareAttr("id", "browser"))
    ) {
      (nodes, selector) => (nodes \ selector._1).filter(selector._2)
    } \ "li" map(node => (node \ "@title").text)

    titles foreach {println}
  }

  class compareAttr(attrPrefix: String, val text: String) extends PartialFunction[Node, Boolean] {
    val attr = "@" + attrPrefix
    override def apply(node: Node):Boolean = if ((node \ attr).text == text) true else false
    override def isDefinedAt(node: Node):Boolean = apply(node)
  }

  object compareAttr {
    def apply(attr: String, test: String): compareAttr = new compareAttr(attr, test)
  }
}

Pair の List を foldLeft でまわす所は、素直に下記のように書いた方が良いきもするのですが、括弧の数が…。

    val titles = (((((xhtml
     \\ "div" filter(compareAttr("id", "browser"))
    ) \ "div" filter(compareAttr("id", "tpl"))
    ) \ "ol"  filter(compareAttr("class", "packages"))
    ) \ "li"  filter(compareAttr("class", "pack"))
    ) \ "ol"  filter(compareAttr("class", "templates") orElse compareAttr("class", "packages"))
    ) \ "li"  map(node => (node \ "@title").text)

うう… XPath 使いたい。

PartialFunction を case を使って定義しなおしてみた。

import scala.io.Source
import scala.xml.{Node, NodeSeq}
import scala.xml.parsing.XhtmlParser

object Test {
  def main(args:Array[String]) = {
    val source = Source.fromFile("/opt/local/share/scala-2.8/doc/scala-devel-docs/api/index.html")
    val xhtml = XhtmlParser(source)
    source.close

    val titles = List(
      "div" -> compareAttr("id", "browser"),
      "div" -> compareAttr("id", "tpl"),
      "ol"  -> compareAttr("class", "packages"),
      "li"  -> compareAttr("class", "pack"),
      "ol"  -> (compareAttr("class", "templates") orElse compareAttr("class", "packages"))
    ).foldLeft (
      xhtml \ "body"
    ) {
      (nodes, selector) => (nodes \ selector._1).filter(selector._2 orElse ignorePattern)
    } \ "li" map(node => (node \ "@title").text)

    titles foreach {println}
  }

  def compareAttr(attrPrefix: String, text: String) = {
    val attr = "@" + attrPrefix
    var pf: PartialFunction[Node, Boolean] = {
      case node if (node \ attr).text == text => true
    }
    pf
  }

  def ignorePattern: PartialFunction[Node, Boolean] = {case _ => false}
}