漢数字パーサだよ

KanjiNumberParser.scala

import scalaz._
import Scalaz._
import scala.util.parsing.combinator._

object KanjiNumberParser extends RegexParsers {

  def one = "一" ^^^ digits(1)
  def two = "二" ^^^ digits(2)
  def three = "三" ^^^ digits(3)
  def four = "四" ^^^ digits(4)
  def five = "五" ^^^ digits(5)
  def six = "六" ^^^ digits(6)
  def seven = "七" ^^^ digits(7)
  def eight = "八" ^^^ digits(8)
  def nine = "九" ^^^ digits(9)

  def oneDigit: Parser[Digit] = one | two | three | four | five | six | seven | eight | nine

  def ju = opt(oneDigit) <~ "十" ^^ { _ | digits(1) }
  def hyaku = opt(oneDigit) <~ "百" ^^ { _ | digits(1) }
  def sen = opt(oneDigit) <~ "千" ^^ { _ | digits(1) }

  def threeDigits = opt(sen) ~ opt(hyaku) ~ opt(ju) ~ opt(oneDigit) ^^ {
    case a ~ b ~ c ~ d => (a +>: b +>: c +>: d +>: nil).map(_.orZero)
  }

  def man = opt(threeDigits) <~ "万" ^^ { _ | 10000L.digits }
  def oku = opt(threeDigits) <~ "億" ^^ { _ | (10000L * 10000L).digits }
  def cho = opt(threeDigits) <~ "兆" ^^ { _ | (10000L * 10000L * 10000L).digits }

  def kanjiNumber = opt(cho) ~ opt(oku) ~ opt(man) ~ opt(threeDigits) ^^ {
    case a ~ b ~ c ~ d => ~(a |+| b |+| c |+| d)
  }

  def parse(in: String) = parseAll(kanjiNumber, in)

}

object Main extends App {
  KanjiNumberParser.parse("千五百兆二千二億三千五百十九万百一").map(_.longDigits assert_=== 1500200235190101L).getOrElse(throw new RuntimeException)
}