Dict.scala

Dict.scala

sealed trait Dict
object Dict {
  // dict(“a”: “apple”, “b”: dict(“c”: “cat”, “d”: “dog”)) -> “{a:apple,b:{c:cat,d:dog}}”
  case class Val(s: String) extends Dict
  case class Obj(m: Map[String, Dict]) extends Dict

  def encode(d: Dict): String = {
    def loop(dd: Dict, sb: StringBuilder): StringBuilder = dd match {
      case Val(s) => sb.append(s)
      case Obj(m) => 
        sb.append("dict(")
        m.foreach { case (k, v) => loop(v, sb.append(k).append(":")).append(",") }
        if (m.nonEmpty) { sb.setLength(sb.length() - 1) }
        sb.append(")")
    }
    
    loop(d, new StringBuilder).toString
  }
}

// Exiting paste mode, now interpreting.

defined trait Dict
defined object Dict

scala> Dict.encode(Dict.Obj(Map("foo" -> Dict.Val("bar"))))
res0: String = dict(foo:bar)

scala> Dict.encode(Dict.Obj(Map("foo" -> Dict.Val("bar"), "baz" -> Dict.Obj(Map("ban" -> Dict.Val("rat"))))))
res2: String = dict(foo:bar,baz:dict(ban:rat))