Simple Non-Polymorphic Stack Machine

gistfile1.scala

import language.implicitConversions
import collection.immutable.Stack
import scalaz._
import Scalaz._

sealed trait Op {
  def execute(ctx: Stack[Int]): Stack[Int]
}

object Op {
  def execute(ctx: Stack[Int], op: Op) = op.execute(ctx)

  implicit def IntToPrimitive(i: Int) = Push(i)
  implicit def ListOpPimp(ops: List[Op]) = new {
    def run = ops.foldLeft(Stack[Int]()) { execute }
  }
}

case class Push(i: Int) extends Op {
  def execute(ctx: Stack[Int]) = ctx.push(i)
}

case class SumOp() extends Op {
  def execute(ctx: Stack[Int]) = {
    val (a, p) = ctx.pop2
    val (b, q) =   p.pop2
    q.push(a + b)
  }
}

object Main extends App {
  import Op._

  val ops = List[Op](2, 3, 5, SumOp(), SumOp())
  val exe = ops.run

  exe.head |> println
}