package v1

sealed abstract class Formula{
  override def toString() = this match {
    case Equals(t1,t2)=> t1.toString+"="+t2.toString
    case NotEquals(t1,t2)=> t1.toString+"!="+t2.toString
  }
}
case class Equals(t1: Term,t2: Term) extends Formula
case class NotEquals(t1: Term, t2: Term) extends Formula

sealed abstract class Term{
 override def toString() = this match {
    case Car(a) => "car("+a.toString+")"
    case Cdr(a) => "cdr("+a.toString+")"
    case Var(a) => a    
    case Null() => "Null"
    case Cons(a,b)=>"cons("+a.toString+","+b.toString+")"    
 }
 }
case class Car(t: Term) extends Term
case class Cdr(t: Term) extends Term
case class Var(n: String) extends Term
case class Null() extends Term
case class Cons(x: Term, t: Term) extends Term
//sealed abstract class MyList extends Term