http://codegolf.stackexchange.com/questions/19151/build-interpreter-for-non-existent-language

interpreter.js

var Token = {
  Concatenate: '0',
  Increment: '1',
  Decrement: '2',
  Multiply: '3',
  Divide: '4',
  Add: '5',
  Subtract: '6',
  Exponent: '7',
  Modulus: '8',
  RotateRight: '9',
  RotateLeft: 'A',
  Duplicate: 'B',
  DoubleDuplicate: 'C',
  Swap: 'D',
  DoubleSwap: 'E',
  Delete: 'F'
};

function parse(input, mem) {
  var a, b, c, d;
  var stack = mem ? mem.slice() : [0];
  for (var i = 0, n = input.length; i < n; i++) {
    switch (input[i]) {
      case Token.Concatenate:
        a = stack.pop();
        b = stack.pop();
        stack.push(parseInt([b] + a));
        break;

      case Token.Increment:
        a = stack.pop();
        stack.push(a + 1);
        break;

      case Token.Decrement:
        a = stack.pop();
        stack.push(a - 1);
        break;

      case Token.Multiply:
        a = stack.pop();
        b = stack.pop();
        stack.push(b * a);
        break;

      case Token.Divide:
        a = stack.pop();
        b = stack.pop();
        stack.push(b / a | 0);
        break;

      case Token.Add:
        a = stack.pop();
        b = stack.pop();
        stack.push(b + a);
        break;

      case Token.Subtract:
        a = stack.pop();
        b = stack.pop();
        stack.push(b - a);
        break;

      case Token.Exponent:
        a = stack.pop();
        b = stack.pop();
        stack.push(Math.pow(b, a));
        break;

      case Token.Modulus:
        a = stack.pop();
        b = stack.pop();
        stack.push(b % a);
        break;

      case Token.RotateRight:
        a = stack.shift();
        stack.push(a);
        break;

      case Token.RotateLeft:
        a = stack.pop();
        stack.unshift(a);
        break;

      case Token.Duplicate:
        a = stack[stack.length - 1];
        stack.push(a);
        break;

      case Token.DoubleDuplicate:
        a = stack[stack.length - 1];
        b = stack[stack.length - 2];
        stack.push(b, a);
        break;

      case Token.Swap:
        a = stack.pop();
        b = stack.pop();
        stack.push(a, b);
        break;

      case Token.DoubleSwap:
        a = stack.pop();
        b = stack.pop();
        c = stack.pop();
        d = stack.pop();
        stack.push(b, a, d, c);
        break;

      case Token.Delete:
        stack.pop();
        break;

      default:
        throw new SynxtaxError('Invalid token "' + input[i] + '"');
    }
  }

  return stack.reverse();
}

exports.Token = Token;
exports.parse = parse;