Brainf*ck interpreter

// Contributed by Daniel Gronau
import scala.annotation._

trait Func[T] {
    val zero: T
    def inc(t: T): T
    def dec(t: T): T
    def in: T
    def out(t: T): Unit
}

object ByteFunc extends Func[Byte] {
  override val zero: Byte = 0
  override def inc(t: Byte) = ((t + 1) & 0xFF).toByte
  override def dec(t: Byte) = ((t - 1) & 0xFF).toByte
  override def in: Byte = readByte
  override def out(t: Byte) { print(t.toChar) }
}

case class Tape[T](left: List[T], cell: T, right: List[T])(implicit func: Func[T]) {
  private def headOf(list:List[T]) = if (list.isEmpty) func.zero else list.head
  private def tailOf(list:List[T]) = if (list.isEmpty) Nil else list.tail
  def isZero = cell == func.zero
  def execute(ch: Char) = (ch: @switch) match {
   case '+' => copy(cell = func.inc(cell))
   case '-' => copy(cell = func.dec(cell))
   case '<' => Tape(tailOf(left), headOf(left), cell :: right)
   case '>' => Tape(cell :: left, headOf(right), tailOf(right))
   case '.' => func.out(cell); this
   case ',' => copy(cell = func.in)
   case '[' | ']' => this
   case _ => error("Unexpected token: " + ch)
  }
}

object Tape {
  def empty[T](func: Func[T]) = Tape(Nil, func.zero, Nil)(func)
}

class Brainfuck[T](func:Func[T]) {

  def execute(p: String) {
    val prog = p.replaceAll("[^\\+\\-\\[\\]\\.\\,\\>\\<]", "")

    @tailrec def braceMatcher(pos: Int, stack: List[Int], o2c: Map[Int, Int]): Map[Int,Int] =
      if(pos == prog.length) o2c else (prog(pos): @switch) match {
        case '[' => braceMatcher(pos + 1, pos :: stack, o2c)
        case ']' => braceMatcher(pos + 1, stack.tail, o2c + (stack.head -> pos))
        case _ => braceMatcher(pos + 1, stack, o2c)
      }

    val open2close = braceMatcher(0, Nil, Map())
    val close2open = open2close.map(_.swap)

    @tailrec def ex(pos:Int, tape:Tape[T]): Unit =
      if(pos < prog.length) ex((prog(pos): @switch) match {
          case '[' if tape.isZero => open2close(pos)
          case ']' if ! tape.isZero => close2open(pos)
          case _ => pos + 1
        }, tape.execute(prog(pos)))

    println("---running---")
    ex(0, Tape.empty(func))
    println("\n---done---")
  }
} 

/*
  Run with:
    val bf = new Brainfuck(ByteFunc)
    bf.execute(""">+++++++++[<++++++++>-]<.>+++++++[<++
                  ++>-]<+.+++++++..+++.[-]>++++++++[<++++>-]
                  <.#>+++++++++++[<+++++>-]<.>++++++++[<++
                  +>-]<.+++.------.--------.[-]>++++++++[<++++>
                  -]<+.[-]++++++++++.""")
*/