Data commit

Task/Execute-Brain-/Scala/execute-brain-.scala

@@ -0,0 +1,65 @@
+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---")
+  }
+}