r.prototype.mul = function() {
  var _len = arguments.length;var _args = new Array(_len); for (var _i = 0; _i < _len; _i++) {_args[_i] = arguments[_i];}
  Term.prototype._arityRange(_args, 2, Infinity, 'r.mul', this);

  var term = new Term(this).expr(_args[0]);