idiomatic way to solve chicken-egg in scala -

how nicely initialize structures that:

case class a(name: string, b: b) case class b(name: string, a: a) 

looking solution without lazy vals (performance overhead) , without adding new members existing case class (it looks ugly), special wrappers , changes of original type-signature maybe fine (at least it's best i've got now). tostring-problem negligible can override in trait.

for now, came this:

   case class chicken[t](h: holder[t, _]) {      def = h.chicken      override def tostring = get.tostring    }     case class egg[u](h: holder[_, u]) {      def = h.egg      override def tostring = get.tostring    }     implicit def egg[t] = (_: egg[t]).get    implicit def chicken[t] = (_: chicken[t]).get     case class holder[u, t] (chickenf: (egg[t], chicken[u]) => (u, t)) {      val (chicken, egg) = chickenf( egg(this), chicken(this))    }     def mutual[u, t](chickenf: (egg[t], chicken[u]) => (u, t)) = {         val h = new holder(chickenf)         h.chicken -> h.egg    }      trait named { //to avoid unfinite tostring        def name: string        override def tostring = name    } 

usage:

case class a(name: string, b: egg[b]) case class b(name: string, a: chicken[a]) extends named  val (a, b) = mutual[a, b](a("a", _) -> b("b", _))  val (a2, b2) = mutual[a, b]{ (b2, a2) => //alternative complex cases     a("a", b2) -> b("b", a2)     }  println(a) println(b) println(a.b) println(b.a) 

results:

a(a,b)                                                                                                                                                                                                                                                  b                                                                                                                                                                                                                                                       b                                                                                                                                                                                                                                                       a(a,b)  

still hope there library that, scalaz or some-macro based solution.