static Double eval()

in spectator-ext-jvm/src/main/java/com/netflix/spectator/jvm/MappingExpr.java [104:126]

• 23 lines of code
• 10 McCabe index (conditional complexity)

  static Double eval(String expr, Map<String, ? extends Number> vars) {
    Deque<Double> stack = new ArrayDeque<>();
    String[] parts = expr.split("[,\\s]+");
    for (String part : parts) {
      switch (part) {
        case ":add":        binaryOp(stack, (a, b) -> a + b); break;
        case ":sub":        binaryOp(stack, (a, b) -> a - b); break;
        case ":mul":        binaryOp(stack, (a, b) -> a * b); break;
        case ":div":        binaryOp(stack, (a, b) -> a / b); break;
        case ":if-changed": ifChanged(stack);                 break;
        default:
          if (part.startsWith("{") && part.endsWith("}")) {
            Number v = vars.get(part.substring(1, part.length() - 1));
            if (v == null) v = Double.NaN;
            stack.addFirst(v.doubleValue());
          } else {
            stack.addFirst(Double.parseDouble(part));
          }
          break;
      }
    }
    return stack.removeFirst();
  }