Scala Calculator

ExprParser.scala

/**
*  This class is used to parse a String and calculate the value of the expression
*  assertEquals( 34,ExprParser.parse("1+2+3+4*3+4",(x:Double)=>x+1))
*/
import scala.util.parsing.combinator._
object ExprParser extends JavaTokenParsers {
    /*
     * text is the input String,func is a function effect on every element
     */
    def parse(text: String, func:  Double => Double ) = {
      def expr = term ~ rep("+" ~ term | "-" ~ term) ^^ {
        case v ~ f => f.foldLeft(v) {
          case (x, "+" ~ term) => x + term
          case (x, "-" ~ term) => x - term
        }
      }
      def term = factor ~ rep("*" ~ factor | "/" ~ factor) ^^ {
        case v ~ f => f.foldLeft(v) {
          case (x, "*" ~ term) => x * term
          case (x, "/" ~ term) => x / term
        }
      }
      def factor: Parser[Double] =
        (floatingPointNumber ^^   { case x => {
           func(x.toString.toDouble)
        }}) | "(" ~> expr <~ ")"
      parseAll(expr, text)
    }
}