old_contents: 
  /**
   * Licensed to the Apache Software Foundation (ASF) under one
   * or more contributor license agreements.  See the NOTICE file
   * distributed with this work for additional information
   * regarding copyright ownership.  The ASF licenses this file
   * to you under the Apache License, Version 2.0 (the
   * "License"); you may not use this file except in compliance
   * with the License.  You may obtain a copy of the License at
   * 
   *   http://www.apache.org/licenses/LICENSE-2.0
   * 
   * Unless required by applicable law or agreed to in writing,
   * software distributed under the License is distributed on an
   * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
   * KIND, either express or implied.  See the License for the
   * specific language governing permissions and limitations
   * under the License.
   **/
  
  "use strict";
  
  const runner = require("./runner");
  
  function Visitor (callback) {
  	this.callback = callback;
  };
  
  Visitor.prototype.get_type = function (item) {
  	return item.constructor.name;
  };
  
  Visitor.prototype.eval = function (skeleton, params) {
  	switch (this.get_type(skeleton)) {
  		case "Seq": 
  			this.eval_seq(skeleton, params); 
  			break;
  	}
  };
  
  Visitor.prototype.eval_seq  = function (skeleton, params) {
  	runner.series(skeleton.execute, params, this.callback);
  };
  
  exports.Visitor = function (callback) {
  	return new Visitor(callback);
  };
  
new_contents: 
  /**
   * Licensed to the Apache Software Foundation (ASF) under one
   * or more contributor license agreements.  See the NOTICE file
   * distributed with this work for additional information
   * regarding copyright ownership.  The ASF licenses this file
   * to you under the Apache License, Version 2.0 (the
   * "License"); you may not use this file except in compliance
   * with the License.  You may obtain a copy of the License at
   * 
   *   http://www.apache.org/licenses/LICENSE-2.0
   * 
   * Unless required by applicable law or agreed to in writing,
   * software distributed under the License is distributed on an
   * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
   * KIND, either express or implied.  See the License for the
   * specific language governing permissions and limitations
   * under the License.
   **/
  
  "use strict";
  
  const runner = require("./runner");
  
  function Visitor (callback) {
  	this.callback = callback;
  };
  
  Visitor.prototype.get_type = function (item) {
  	return item.constructor.name;
  };
  
  Visitor.prototype.eval = function (skeleton, params) {
  	switch (this.get_type(skeleton)) {
  		case "Seq": 
  			this.eval_seq(skeleton, params); 
  			break;
  		case "Map": 
  			this.eval_map(skeleton, params); 
  			break;
  	}
  };
  
  Visitor.prototype.eval_seq  = function (skeleton, params) {
  	runner.series(skeleton.execute, params, this.callback);
  };
  
  Visitor.prototype.eval_map  = function (skeleton, params) {
  	runner.map(skeleton.execute, params, this.callback);
  };
  
  exports.Visitor = function (callback) {
  	return new Visitor(callback);
  };
  
subject: Update visitor.js