QuotedString.scala

final class QuotedString(private val sc: StringContext) extends AnyVal {
  /**
   * {{{
   * scala> val msg = "foo"
   * msg: String = foo
   *
   * scala> qs"$msg"
   * res1: String = "foo"
   *
   * scala> qs"<$msg"
   * res2: String = <"foo"
   *
   * scala> qs"<$msg>"
   * res3: String = <"foo">
   *
   * scala> qs"$msg>"
   * res4: String = "foo">
   * }}}
   */
  def qs(vars: Any*): String = {
    def interleave[A](xs: Iterable[String], ys: Iterable[Any]): String = {
      val sbldr = new StringBuilder()
      val xiter = xs.iterator
      val yiter = ys.iterator

      while (xiter.hasNext) {
        sbldr ++= xiter.next()

        if (yiter.hasNext) {
          sbldr += '"'
          sbldr ++= yiter.next().toString
          sbldr += '"'
        }
      }

      sbldr.mkString
    }

    interleave(sc.parts, vars)
  }
}