SigmaBoolean

  /** Algebraic data type of sigma proposition expressions.
    * Values of this type are used as values of SigmaProp type of SigmaScript and SigmaDsl
    */
  trait SigmaBoolean {
    /** Unique id of the node class used in serialization of SigmaBoolean. */
    val opCode: OpCode
    /** Size of the proposition tree (number of nodes). */
    def size: Int
  }

From Values.scala