scala で awk っぽいの

sawk.scala

package sawk

import scala.io.Source
import scala.collection.mutable.Map

object Sawk {
  def apply(script: SawkScript): Unit = {
    script.run
  }
}

abstract class SawkScript(lines: Iterator[String], val FS: String = "\t") {

  private var _main: (String, List[String]) => Unit = (x, xs) => ()
  private var _begin: () => Unit = () => ()
  private var _end: () => Unit = () => ()

  def BEGIN(f: => Unit): Unit = {
    _begin = () => f
  }

  def MAIN(f: (String, List[String]) => Unit): Unit = {
    _main = f
  }

  def run(): Unit = {
    _begin.apply
    lines.foreach { l =>
      val line = l
      val fields = l.split(FS).toList
      _main.apply(line, fields)
    }
    _end.apply
  }

  def END(f: => Unit): Unit = {
    _end = () => f
  }

}


// awk スクリプト
class CountUpScript(lines: Iterator[String]) extends SawkScript(lines) {

  var data: Map[String, Int] = Map.empty.withDefaultValue(0)

  BEGIN {
    println("合計を計算します")
  }

  // line: 現在行
  // line: 現在行をFSで分割したフィールド
  MAIN { (line, fields) =>
    data(fields(0)) += fields(1).toInt
  }

  END {
    data.map { case (k, v) => k + "\t" + v }.foreach(println)
  }

}

object Main {

  def main(args: Array[String]): Unit = {

    val data="""|りんご	1
                |りんご	3
                |みかん	2
                |りんご	4
                |みかん	5
                |なし	3
                |""".stripMargin

    val awkScript = new CountUpScript(data.lines)
    Sawk(awkScript)


    /*

     Output:

     合計を計算します
     なし    3
     みかん  7
     りんご  8

     */
  }
}