Simple math interpreter

gistfile1.scala

object Interpreter {
  def main(args:Array[String]) = {
    (new SimpleParser).parseString("2*3.2 + 3*(36.07/4 - 10)").println
  }

  import scala.util.parsing.combinator._
  class SimpleParser extends JavaTokenParsers {
    def expr: Parser[Double] = (
        term~"+"~expr ^^ { case a~"+"~b => a + b }
      | term~"-"~expr ^^ { case a~"-"~b => a - b }
      | term)
    def term: Parser[Double] = (
        num~"*"~term ^^ { case a~"*"~b => a * b}
      | num~"/"~term ^^ { case a~"/"~b => a / b}
      | num)
    def num: Parser[Double] =
      floatingPointNumber ^^ (_.toDouble) |
      "("~expr~")" ^^ { case "("~a~")" => a }
    def parseString = parseAll(expr, (_:String)) match {
      case Success(result,_) => "Result: %.4f" format result
      case Failure(msg, _) => "Parsing failed: %s" format msg
    }
  }

} /*