Initial data commit

Task/Parsing-RPN-calculator-algorithm/Scala/parsing-rpn-calculator-algorithm.scala

@@ -0,0 +1,40 @@
+object RPN {
+  val PRINT_STACK_CONTENTS: Boolean = true
+
+  def main(args: Array[String]): Unit = {
+    val result = evaluate("3 4 2 * 1 5 - 2 3 ^ ^ / +".split(" ").toList)
+    println("Answer: " + result)
+  }
+
+  def evaluate(tokens: List[String]): Double = {
+    import scala.collection.mutable.Stack
+    val stack: Stack[Double] = new Stack[Double]
+    for (token <- tokens) {
+      if (isOperator(token)) token match {
+        case "+" => stack.push(stack.pop + stack.pop)
+        case "-" => val x = stack.pop; stack.push(stack.pop - x)
+        case "*" => stack.push(stack.pop * stack.pop)
+        case "/" => val x = stack.pop; stack.push(stack.pop / x)
+        case "^" => val x = stack.pop; stack.push(math.pow(stack.pop, x))
+        case _ => throw new RuntimeException( s""""$token" is not an operator""")
+      }
+      else stack.push(token.toDouble)
+
+      if (PRINT_STACK_CONTENTS) {
+        print("Input: " + token)
+        print(" Stack: ")
+        for (element <- stack.seq.reverse) print(element + " ");
+        println("")
+      }
+    }
+
+    stack.pop
+  }
+
+  def isOperator(token: String): Boolean = {
+    token match {
+      case "+" => true; case "-" => true; case "*" => true; case "/" => true; case "^" => true
+      case _ => false
+    }
+  }
+}