# JSDoc: Source: lib/browser_jools.js

# Source: lib/browser_jools.js

    /**
     * @namespace browser_jools
     */

    /**
     * @memberof browser_jools
     * @param file
     * @param cwd
     */
    var require = function (file, cwd) {
        var resolved = require.resolve(file, cwd || '/');
        var mod = require.modules[resolved];
        if (!mod) throw new Error(
            'Failed to resolve module ' + file + ', tried ' + resolved
        );
        var res = mod._cached ? mod._cached : mod();
        return res;
    }

    require.paths = [];
    require.modules = {};
    require.extensions = [".js",".coffee"];

    require._core = {
        'assert': true,
        'events': true,
        'fs': true,
        'path': true,
        'vm': true
    };
    /**
     * @memberof browser_jools
     */
    require.resolve = (function () {
        return function (x, cwd) {
            if (!cwd) cwd = '/';

            if (require._core[x]) return x;
            var path = require.modules.path();
            cwd = path.resolve('/', cwd);
            var y = cwd || '/';

            if (x.match(/^(?:\.\.?\/|\/)/)) {
                var m = loadAsFileSync(path.resolve(y, x))
                    || loadAsDirectorySync(path.resolve(y, x));
                if (m) return m;
            }

            var n = loadNodeModulesSync(x, y);
            if (n) return n;

            throw new Error("Cannot find module '" + x + "'");

            function loadAsFileSync (x) {
                if (require.modules[x]) {
                    return x;
                }

                for (var i = 0; i < require.extensions.length; i++) {
                    var ext = require.extensions[i];
                    if (require.modules[x + ext]) return x + ext;
                }
            }

            function loadAsDirectorySync (x) {
                x = x.replace(/\/+$/, '');
                var pkgfile = x + '/package.json';
                if (require.modules[pkgfile]) {
                    var pkg = require.modules[pkgfile]();
                    var b = pkg.browserify;
                    if (typeof b === 'object' && b.main) {
                        var m = loadAsFileSync(path.resolve(x, b.main));
                        if (m) return m;
                    }
                    else if (typeof b === 'string') {
                        var m = loadAsFileSync(path.resolve(x, b));
                        if (m) return m;
                    }
                    else if (pkg.main) {
                        var m = loadAsFileSync(path.resolve(x, pkg.main));
                        if (m) return m;
                    }
                }

                return loadAsFileSync(x + '/index');
            }

            function loadNodeModulesSync (x, start) {
                var dirs = nodeModulesPathsSync(start);
                for (var i = 0; i < dirs.length; i++) {
                    var dir = dirs[i];
                    var m = loadAsFileSync(dir + '/' + x);
                    if (m) return m;
                    var n = loadAsDirectorySync(dir + '/' + x);
                    if (n) return n;
                }

                var m = loadAsFileSync(x);
                if (m) return m;
            }

            function nodeModulesPathsSync (start) {
                var parts;
                if (start === '/') parts = [ '' ];
                else parts = path.normalize(start).split('/');

                var dirs = [];
                for (var i = parts.length - 1; i >= 0; i--) {
                    if (parts[i] === 'node_modules') continue;
                    var dir = parts.slice(0, i + 1).join('/') + '/node_modules';
                    dirs.push(dir);
                }

                return dirs;
            }
        };
    })();
    /**
     * @memberof browser_jools
     */
    require.alias = function (from, to) {
        var path = require.modules.path();
        var res = null;
        try {
            res = require.resolve(from + '/package.json', '/');
        }
        catch (err) {
            res = require.resolve(from, '/');
        }
        var basedir = path.dirname(res);

        var keys = (Object.keys || function (obj) {
            var res = [];
            for (var key in obj) res.push(key)
            return res;
        })(require.modules);

        for (var i = 0; i < keys.length; i++) {
            var key = keys[i];
            if (key.slice(0, basedir.length + 1) === basedir + '/') {
                var f = key.slice(basedir.length);
                require.modules[to + f] = require.modules[basedir + f];
            }
            else if (key === basedir) {
                require.modules[to] = require.modules[basedir];
            }
        }
    };
    /**
     * @memberof browser_jools
     */
    require.define = function (filename, fn) {
        var dirname = require._core[filename]
            ? ''
            : require.modules.path().dirname(filename)
        ;

        var require_ = function (file) {
            return require(file, dirname)
        };
        require_.resolve = function (name) {
            return require.resolve(name, dirname);
        };
        require_.modules = require.modules;
        require_.define = require.define;
        var module_ = { exports : {} };

        require.modules[filename] = function () {
            require.modules[filename]._cached = module_.exports;
            fn.call(
                module_.exports,
                require_,
                module_,
                module_.exports,
                dirname,
                filename
            );
            require.modules[filename]._cached = module_.exports;
            return module_.exports;
        };
    };

    if (typeof process === 'undefined') process = {};

    if (!process.nextTick) process.nextTick = (function () {
        var queue = [];
        var canPost = typeof window !== 'undefined'
            && window.postMessage && window.addEventListener
        ;

        if (canPost) {
            window.addEventListener('message', function (ev) {
                if (ev.source === window && ev.data === 'browserify-tick') {
                    ev.stopPropagation();
                    if (queue.length > 0) {
                        var fn = queue.shift();
                        fn();
                    }
                }
            }, true);
        }

        return function (fn) {
            if (canPost) {
                queue.push(fn);
                window.postMessage('browserify-tick', '*');
            }
            else setTimeout(fn, 0);
        };
    })();

    if (!process.title) process.title = 'browser';

    if (!process.binding) process.binding = function (name) {
        if (name === 'evals') return require('vm')
        else throw new Error('No such module')
    };

    if (!process.cwd) process.cwd = function () { return '.' };

    if (!process.env) process.env = {};
    if (!process.argv) process.argv = [];

    require.define("path", function (require, module, exports, __dirname, __filename) {
    function filter (xs, fn) {
        var res = [];
        for (var i = 0; i < xs.length; i++) {
            if (fn(xs[i], i, xs)) res.push(xs[i]);
        }
        return res;
    }

    /**
     * resolves . and .. elements in a path array with directory names there
     * must be no slashes, empty elements, or device names (c:\) in the array
     * (so also no leading and trailing slashes - it does not distinguish
     * relative and absolute paths)
     * @memberof browser_jools
     * @param parts
     * @param allowAboveRoot
     */
    function normalizeArray(parts, allowAboveRoot) {
      // if the path tries to go above the root, `up` ends up > 0
      var up = 0;
      for (var i = parts.length; i >= 0; i--) {
        var last = parts[i];
        if (last == '.') {
          parts.splice(i, 1);
        } else if (last === '..') {
          parts.splice(i, 1);
          up++;
        } else if (up) {
          parts.splice(i, 1);
          up--;
        }
      }

      // if the path is allowed to go above the root, restore leading ..s
      if (allowAboveRoot) {
        for (; up--; up) {
          parts.unshift('..');
        }
      }

      return parts;
    }

    // Regex to split a filename into [*, dir, basename, ext]
    // posix version
    var splitPathRe = /^(.+\/(?!$)|\/)?((?:.+?)?(\.[^.]*)?)$/;

    // path.resolve([from ...], to)
    // posix version
    exports.resolve = function() {
    var resolvedPath = '',
        resolvedAbsolute = false;

    for (var i = arguments.length; i >= -1 && !resolvedAbsolute; i--) {
      var path = (i >= 0)
          ? arguments[i]
          : process.cwd();

      // Skip empty and invalid entries
      if (typeof path !== 'string' || !path) {
        continue;
      }

      resolvedPath = path + '/' + resolvedPath;
      resolvedAbsolute = path.charAt(0) === '/';
    }

    // At this point the path should be resolved to a full absolute path, but
    // handle relative paths to be safe (might happen when process.cwd() fails)

    // Normalize the path
    resolvedPath = normalizeArray(filter(resolvedPath.split('/'), function(p) {
        return !!p;
      }), !resolvedAbsolute).join('/');

      return ((resolvedAbsolute ? '/' : '') + resolvedPath) || '.';
    };

    // path.normalize(path)
    // posix version
    exports.normalize = function(path) {
    var isAbsolute = path.charAt(0) === '/',
        trailingSlash = path.slice(-1) === '/';

    // Normalize the path
    path = normalizeArray(filter(path.split('/'), function(p) {
        return !!p;
      }), !isAbsolute).join('/');

      if (!path && !isAbsolute) {
        path = '.';
      }
      if (path && trailingSlash) {
        path += '/';
      }

      return (isAbsolute ? '/' : '') + path;
    };

    // posix version
    exports.join = function() {
      var paths = Array.prototype.slice.call(arguments, 0);
      return exports.normalize(filter(paths, function(p, index) {
        return p && typeof p === 'string';
      }).join('/'));
    };

    exports.dirname = function(path) {
      var dir = splitPathRe.exec(path)[1] || '';
      var isWindows = false;
      if (!dir) {
        // No dirname
        return '.';
      } else if (dir.length === 1 ||
          (isWindows && dir.length <= 3 && dir.charAt(1) === ':')) {
        // It is just a slash or a drive letter with a slash
        return dir;
      } else {
        // It is a full dirname, strip trailing slash
        return dir.substring(0, dir.length - 1);
      }
    };

    exports.basename = function(path, ext) {
      var f = splitPathRe.exec(path)[2] || '';
      // TODO: make this comparison case-insensitive on windows?
      if (ext && f.substr(-1 * ext.length) === ext) {
        f = f.substr(0, f.length - ext.length);
      }
      return f;
    };

    exports.extname = function(path) {
      return splitPathRe.exec(path)[3] || '';
    };

    });

    require.define("/node_modules/jools/package.json", function (require, module, exports, __dirname, __filename) {
    module.exports = {"main":"./lib/jools"}
    });

    require.define("/node_modules/jools/lib/jools.js", function (require, module, exports, __dirname, __filename) {
    /**
     * Module dependencies.
     */
    var utils = require('./utils')
      , _ = require('underscore');

    /**
     * version
     * @memberof browser_jools
     */
    exports.version = '0.0.1';

    /**
     * Jools constructor.
     *
     * A rule consists of:
     *   - Descriptive name
     *   - One or more conditions
     *   - One or more consequences, which are fired when all conditions evaluate to true.
     * @memberof browser_jools
     * @param {Object} rules
     */
    function Jools(rules) {
      this.rules = rules;
    }

    /**
     * execute rules with fact
     *
     * @param {Object} fact
     */
    Jools.prototype.execute = function (fact) {
      var self = this
        , session = _.clone(fact)
        , last_session = _.clone(fact)
        , goal = false;

      while (!goal) {
        var changes = false;
        for (var x=0; x < this.rules.length; x++) {
          var rule = this.rules[x]
            , outcome;

          _.flatten([rule.condition]).forEach(function (cnd) {
            cnd.__args = cnd.__args || utils.paramNames(cnd);

            if (outcome) {
              outcome = outcome && cnd.apply({}, utils.paramsToArguments(session, cnd.__args));
            } else {
              outcome = cnd.apply({}, utils.paramsToArguments(session, cnd.__args));
            }
          });
          if (outcome) {
            _.flatten([rule.consequence]).forEach(function (csq) {
              csq.__args = csq.__args || utils.paramNames(csq);
              csq.apply(session, utils.paramsToArguments(fact, csq.__args));
              if (!_.isEqual(last_session,session)) {
                // Fire all rules again!
                changes = true;
                last_session = _.clone(session);
              }
            });
          }
          if(changes) break;
        }
        if (!changes) goal = true;
      }
      return session;
    };

    module.exports = Jools;

    });

    require.define("/node_modules/jools/lib/utils.js", function (require, module, exports, __dirname, __filename) {
    /**
     * Returns an array of parameter names of the function f
     * @memberof browser_jools
     * @param {Function} f
     */
    module.exports.paramNames = function (f) {
      var m = /function[^\(]*\(([^\)]*)\)/.exec(f.toString());
      if (!m) throw new TypeError("Invalid functions");

      var params = [];
      m[1].split(',').forEach(function (p) {
        params.push(p.replace(/^\s*|\s*$/g, ''));
      });

      return params;
    };

    /**
     * Creates an array of arguments
     * @memberof browser_jools
     * @param {Object} obj
     * @param {Array} params
     */
    module.exports.paramsToArguments = function (obj, params) {
      var args = [];
      params.forEach(function (p) {
        args.push(obj[p]);
      });
      return args;
    }

    });

    require.define("/node_modules/underscore/package.json", function (require, module, exports, __dirname, __filename) {
    module.exports = {"main":"underscore.js"}
    });

    require.define("/node_modules/underscore/underscore.js", function (require, module, exports, __dirname, __filename) {
    //     Underscore.js 1.3.3
    //     (c) 2009-2012 Jeremy Ashkenas, DocumentCloud Inc.
    //     Underscore is freely distributable under the MIT license.
    //     Portions of Underscore are inspired or borrowed from Prototype,
    //     Oliver Steele's Functional, and John Resig's Micro-Templating.
    //     For all details and documentation:
    //     http://documentcloud.github.com/underscore

    (function() {

      // Baseline setup
      // --------------

      // Establish the root object, `window` in the browser, or `global` on the server.
      var root = this;

      // Save the previous value of the `_` variable.
      var previousUnderscore = root._;

      // Establish the object that gets returned to break out of a loop iteration.
      var breaker = {};

      // Save bytes in the minified (but not gzipped) version:
      var ArrayProto = Array.prototype, ObjProto = Object.prototype, FuncProto = Function.prototype;

      // Create quick reference variables for speed access to core prototypes.
      var slice            = ArrayProto.slice,
          unshift          = ArrayProto.unshift,
          toString         = ObjProto.toString,
          hasOwnProperty   = ObjProto.hasOwnProperty;

      // All **ECMAScript 5** native function implementations that we hope to use
      // are declared here.
      var
        nativeForEach      = ArrayProto.forEach,
        nativeMap          = ArrayProto.map,
        nativeReduce       = ArrayProto.reduce,
        nativeReduceRight  = ArrayProto.reduceRight,
        nativeFilter       = ArrayProto.filter,
        nativeEvery        = ArrayProto.every,
        nativeSome         = ArrayProto.some,
        nativeIndexOf      = ArrayProto.indexOf,
        nativeLastIndexOf  = ArrayProto.lastIndexOf,
        nativeIsArray      = Array.isArray,
        nativeKeys         = Object.keys,
        nativeBind         = FuncProto.bind;

      // Create a safe reference to the Underscore object for use below.
      var _ = function(obj) { return new wrapper(obj); };

      // Export the Underscore object for **Node.js**, with
      // backwards-compatibility for the old `require()` API. If we're in
      // the browser, add `_` as a global object via a string identifier,
      // for Closure Compiler "advanced" mode.
      if (typeof exports !== 'undefined') {
        if (typeof module !== 'undefined' && module.exports) {
          exports = module.exports = _;
        }
        exports._ = _;
      } else {
        root['_'] = _;
      }

      // Current version.
      _.VERSION = '1.3.3';

      // Collection Functions
      // --------------------

      // The cornerstone, an `each` implementation, aka `forEach`.
      // Handles objects with the built-in `forEach`, arrays, and raw objects.
      // Delegates to **ECMAScript 5**'s native `forEach` if available.
      var each = _.each = _.forEach = function(obj, iterator, context) {
        if (obj == null) return;
        if (nativeForEach && obj.forEach === nativeForEach) {
          obj.forEach(iterator, context);
        } else if (obj.length === +obj.length) {
          for (var i = 0, l = obj.length; i < l; i++) {
            if (i in obj && iterator.call(context, obj[i], i, obj) === breaker) return;
          }
        } else {
          for (var key in obj) {
            if (_.has(obj, key)) {
              if (iterator.call(context, obj[key], key, obj) === breaker) return;
            }
          }
        }
      };

      // Return the results of applying the iterator to each element.
      // Delegates to **ECMAScript 5**'s native `map` if available.
      _.map = _.collect = function(obj, iterator, context) {
        var results = [];
        if (obj == null) return results;
        if (nativeMap && obj.map === nativeMap) return obj.map(iterator, context);
        each(obj, function(value, index, list) {
          results[results.length] = iterator.call(context, value, index, list);
        });
        if (obj.length === +obj.length) results.length = obj.length;
        return results;
      };

      // **Reduce** builds up a single result from a list of values, aka `inject`,
      // or `foldl`. Delegates to **ECMAScript 5**'s native `reduce` if available.
      _.reduce = _.foldl = _.inject = function(obj, iterator, memo, context) {
        var initial = arguments.length > 2;
        if (obj == null) obj = [];
        if (nativeReduce && obj.reduce === nativeReduce) {
          if (context) iterator = _.bind(iterator, context);
          return initial ? obj.reduce(iterator, memo) : obj.reduce(iterator);
        }
        each(obj, function(value, index, list) {
          if (!initial) {
            memo = value;
            initial = true;
          } else {
            memo = iterator.call(context, memo, value, index, list);
          }
        });
        if (!initial) throw new TypeError('Reduce of empty array with no initial value');
        return memo;
      };

      // The right-associative version of reduce, also known as `foldr`.
      // Delegates to **ECMAScript 5**'s native `reduceRight` if available.
      _.reduceRight = _.foldr = function(obj, iterator, memo, context) {
        var initial = arguments.length > 2;
        if (obj == null) obj = [];
        if (nativeReduceRight && obj.reduceRight === nativeReduceRight) {
          if (context) iterator = _.bind(iterator, context);
          return initial ? obj.reduceRight(iterator, memo) : obj.reduceRight(iterator);
        }
        var reversed = _.toArray(obj).reverse();
        if (context && !initial) iterator = _.bind(iterator, context);
        return initial ? _.reduce(reversed, iterator, memo, context) : _.reduce(reversed, iterator);
      };

      // Return the first value which passes a truth test. Aliased as `detect`.
      _.find = _.detect = function(obj, iterator, context) {
        var result;
        any(obj, function(value, index, list) {
          if (iterator.call(context, value, index, list)) {
            result = value;
            return true;
          }
        });
        return result;
      };

      // Return all the elements that pass a truth test.
      // Delegates to **ECMAScript 5**'s native `filter` if available.
      // Aliased as `select`.
      _.filter = _.select = function(obj, iterator, context) {
        var results = [];
        if (obj == null) return results;
        if (nativeFilter && obj.filter === nativeFilter) return obj.filter(iterator, context);
        each(obj, function(value, index, list) {
          if (iterator.call(context, value, index, list)) results[results.length] = value;
        });
        return results;
      };

      // Return all the elements for which a truth test fails.
      _.reject = function(obj, iterator, context) {
        var results = [];
        if (obj == null) return results;
        each(obj, function(value, index, list) {
          if (!iterator.call(context, value, index, list)) results[results.length] = value;
        });
        return results;
      };

      // Determine whether all of the elements match a truth test.
      // Delegates to **ECMAScript 5**'s native `every` if available.
      // Aliased as `all`.
      _.every = _.all = function(obj, iterator, context) {
        var result = true;
        if (obj == null) return result;
        if (nativeEvery && obj.every === nativeEvery) return obj.every(iterator, context);
        each(obj, function(value, index, list) {
          if (!(result = result && iterator.call(context, value, index, list))) return breaker;
        });
        return !!result;
      };

      // Determine if at least one element in the object matches a truth test.
      // Delegates to **ECMAScript 5**'s native `some` if available.
      // Aliased as `any`.
      var any = _.some = _.any = function(obj, iterator, context) {
        iterator || (iterator = _.identity);
        var result = false;
        if (obj == null) return result;
        if (nativeSome && obj.some === nativeSome) return obj.some(iterator, context);
        each(obj, function(value, index, list) {
          if (result || (result = iterator.call(context, value, index, list))) return breaker;
        });
        return !!result;
      };

      // Determine if a given value is included in the array or object using `===`.
      // Aliased as `contains`.
      _.include = _.contains = function(obj, target) {
        var found = false;
        if (obj == null) return found;
        if (nativeIndexOf && obj.indexOf === nativeIndexOf) return obj.indexOf(target) != -1;
        found = any(obj, function(value) {
          return value === target;
        });
        return found;
      };

      // Invoke a method (with arguments) on every item in a collection.
      _.invoke = function(obj, method) {
        var args = slice.call(arguments, 2);
        return _.map(obj, function(value) {
          return (_.isFunction(method) ? method || value : value[method]).apply(value, args);
        });
      };

      // Convenience version of a common use case of `map`: fetching a property.
      _.pluck = function(obj, key) {
        return _.map(obj, function(value){ return value[key]; });
      };

      // Return the maximum element or (element-based computation).
      _.max = function(obj, iterator, context) {
        if (!iterator && _.isArray(obj) && obj[0] === +obj[0]) return Math.max.apply(Math, obj);
        if (!iterator && _.isEmpty(obj)) return -Infinity;
        var result = {computed : -Infinity};
        each(obj, function(value, index, list) {
          var computed = iterator ? iterator.call(context, value, index, list) : value;
          computed >= result.computed && (result = {value : value, computed : computed});
        });
        return result.value;
      };

      // Return the minimum element (or element-based computation).
      _.min = function(obj, iterator, context) {
        if (!iterator && _.isArray(obj) && obj[0] === +obj[0]) return Math.min.apply(Math, obj);
        if (!iterator && _.isEmpty(obj)) return Infinity;
        var result = {computed : Infinity};
        each(obj, function(value, index, list) {
          var computed = iterator ? iterator.call(context, value, index, list) : value;
          computed < result.computed && (result = {value : value, computed : computed});
        });
        return result.value;
      };

      // Shuffle an array.
      _.shuffle = function(obj) {
        var shuffled = [], rand;
        each(obj, function(value, index, list) {
          rand = Math.floor(Math.random() * (index + 1));
          shuffled[index] = shuffled[rand];
          shuffled[rand] = value;
        });
        return shuffled;
      };

      // Sort the object's values by a criterion produced by an iterator.
      _.sortBy = function(obj, val, context) {
        var iterator = _.isFunction(val) ? val : function(obj) { return obj[val]; };
        return _.pluck(_.map(obj, function(value, index, list) {
          return {
            value : value,
            criteria : iterator.call(context, value, index, list)
          };
        }).sort(function(left, right) {
          var a = left.criteria, b = right.criteria;
          if (a === void 0) return 1;
          if (b === void 0) return -1;
          return a < b ? -1 : a > b ? 1 : 0;
        }), 'value');
      };

      // Groups the object's values by a criterion. Pass either a string attribute
      // to group by, or a function that returns the criterion.
      _.groupBy = function(obj, val) {
        var result = {};
        var iterator = _.isFunction(val) ? val : function(obj) { return obj[val]; };
        each(obj, function(value, index) {
          var key = iterator(value, index);
          (result[key] || (result[key] = [])).push(value);
        });
        return result;
      };

      // Use a comparator function to figure out at what index an object should
      // be inserted so as to maintain order. Uses binary search.
      _.sortedIndex = function(array, obj, iterator) {
        iterator || (iterator = _.identity);
        var low = 0, high = array.length;
        while (low < high) {
          var mid = (low + high) >> 1;
          iterator(array[mid]) < iterator(obj) ? low = mid + 1 : high = mid;
        }
        return low;
      };

      // Safely convert anything iterable into a real, live array.
      _.toArray = function(obj) {
        if (!obj)                                     return [];
        if (_.isArray(obj))                           return slice.call(obj);
        if (_.isArguments(obj))                       return slice.call(obj);
        if (obj.toArray && _.isFunction(obj.toArray)) return obj.toArray();
        return _.values(obj);
      };

      // Return the number of elements in an object.
      _.size = function(obj) {
        return _.isArray(obj) ? obj.length : _.keys(obj).length;
      };

      // Array Functions
      // ---------------

      // Get the first element of an array. Passing **n** will return the first N
      // values in the array. Aliased as `head` and `take`. The **guard** check
      // allows it to work with `_.map`.
      _.first = _.head = _.take = function(array, n, guard) {
        return (n != null) && !guard ? slice.call(array, 0, n) : array[0];
      };

      // Returns everything but the last entry of the array. Especcialy useful on
      // the arguments object. Passing **n** will return all the values in
      // the array, excluding the last N. The **guard** check allows it to work with
      // `_.map`.
      _.initial = function(array, n, guard) {
        return slice.call(array, 0, array.length - ((n == null) || guard ? 1 : n));
      };

      // Get the last element of an array. Passing **n** will return the last N
      // values in the array. The **guard** check allows it to work with `_.map`.
      _.last = function(array, n, guard) {
        if ((n != null) && !guard) {
          return slice.call(array, Math.max(array.length - n, 0));
        } else {
          return array[array.length - 1];
        }
      };

      // Returns everything but the first entry of the array. Aliased as `tail`.
      // Especially useful on the arguments object. Passing an **index** will return
      // the rest of the values in the array from that index onward. The **guard**
      // check allows it to work with `_.map`.
      _.rest = _.tail = function(array, index, guard) {
        return slice.call(array, (index == null) || guard ? 1 : index);
      };

      // Trim out all falsy values from an array.
      _.compact = function(array) {
        return _.filter(array, function(value){ return !!value; });
      };

      // Return a completely flattened version of an array.
      _.flatten = function(array, shallow) {
        return _.reduce(array, function(memo, value) {
          if (_.isArray(value)) return memo.concat(shallow ? value : _.flatten(value));
          memo[memo.length] = value;
          return memo;
        }, []);
      };

      // Return a version of the array that does not contain the specified value(s).
      _.without = function(array) {
        return _.difference(array, slice.call(arguments, 1));
      };

      // Produce a duplicate-free version of the array. If the array has already
      // been sorted, you have the option of using a faster algorithm.
      // Aliased as `unique`.
      _.uniq = _.unique = function(array, isSorted, iterator) {
        var initial = iterator ? _.map(array, iterator) : array;
        var results = [];
        // The `isSorted` flag is irrelevant if the array only contains two elements.
        if (array.length < 3) isSorted = true;
        _.reduce(initial, function (memo, value, index) {
          if (isSorted ? _.last(memo) !== value || !memo.length : !_.include(memo, value)) {
            memo.push(value);
            results.push(array[index]);
          }
          return memo;
        }, []);
        return results;
      };

      // Produce an array that contains the union: each distinct element from all of
      // the passed-in arrays.
      _.union = function() {
        return _.uniq(_.flatten(arguments, true));
      };

      // Produce an array that contains every item shared between all the
      // passed-in arrays. (Aliased as "intersect" for back-compat.)
      _.intersection = _.intersect = function(array) {
        var rest = slice.call(arguments, 1);
        return _.filter(_.uniq(array), function(item) {
          return _.every(rest, function(other) {
            return _.indexOf(other, item) >= 0;
          });
        });
      };

      // Take the difference between one array and a number of other arrays.
      // Only the elements present in just the first array will remain.
      _.difference = function(array) {
        var rest = _.flatten(slice.call(arguments, 1), true);
        return _.filter(array, function(value){ return !_.include(rest, value); });
      };

      // Zip together multiple lists into a single array -- elements that share
      // an index go together.
      _.zip = function() {
        var args = slice.call(arguments);
        var length = _.max(_.pluck(args, 'length'));
        var results = new Array(length);
        for (var i = 0; i < length; i++) results[i] = _.pluck(args, "" + i);
        return results;
      };

      // If the browser doesn't supply us with indexOf (I'm looking at you, **MSIE**),
      // we need this function. Return the position of the first occurrence of an
      // item in an array, or -1 if the item is not included in the array.
      // Delegates to **ECMAScript 5**'s native `indexOf` if available.
      // If the array is large and already in sort order, pass `true`
      // for **isSorted** to use binary search.
      _.indexOf = function(array, item, isSorted) {
        if (array == null) return -1;
        var i, l;
        if (isSorted) {
          i = _.sortedIndex(array, item);
          return array[i] === item ? i : -1;
        }
        if (nativeIndexOf && array.indexOf === nativeIndexOf) return array.indexOf(item);
        for (i = 0, l = array.length; i < l; i++) if (i in array && array[i] === item) return i;
        return -1;
      };

      // Delegates to **ECMAScript 5**'s native `lastIndexOf` if available.
      _.lastIndexOf = function(array, item) {
        if (array == null) return -1;
        if (nativeLastIndexOf && array.lastIndexOf === nativeLastIndexOf) return array.lastIndexOf(item);
        var i = array.length;
        while (i--) if (i in array && array[i] === item) return i;
        return -1;
      };

      // Generate an integer Array containing an arithmetic progression. A port of
      // the native Python `range()` function. See
      // [the Python documentation](http://docs.python.org/library/functions.html#range).
      _.range = function(start, stop, step) {
        if (arguments.length <= 1) {
          stop = start || 0;
          start = 0;
        }
        step = arguments[2] || 1;

        var len = Math.max(Math.ceil((stop - start) / step), 0);
        var idx = 0;
        var range = new Array(len);

        while(idx < len) {
          range[idx++] = start;
          start += step;
        }

        return range;
      };

      // Function (ahem) Functions
      // ------------------

      // Reusable constructor function for prototype setting.
      var ctor = function(){};

      // Create a function bound to a given object (assigning `this`, and arguments,
      // optionally). Binding with arguments is also known as `curry`.
      // Delegates to **ECMAScript 5**'s native `Function.bind` if available.
      // We check for `func.bind` first, to fail fast when `func` is undefined.
      _.bind = function bind(func, context) {
        var bound, args;
        if (func.bind === nativeBind && nativeBind) return nativeBind.apply(func, slice.call(arguments, 1));
        if (!_.isFunction(func)) throw new TypeError;
        args = slice.call(arguments, 2);
        return bound = function() {
          if (!(this instanceof bound)) return func.apply(context, args.concat(slice.call(arguments)));
          ctor.prototype = func.prototype;
          var self = new ctor;
          var result = func.apply(self, args.concat(slice.call(arguments)));
          if (Object(result) === result) return result;
          return self;
        };
      };

      // Bind all of an object's methods to that object. Useful for ensuring that
      // all callbacks defined on an object belong to it.
      _.bindAll = function(obj) {
        var funcs = slice.call(arguments, 1);
        if (funcs.length == 0) funcs = _.functions(obj);
        each(funcs, function(f) { obj[f] = _.bind(obj[f], obj); });
        return obj;
      };

      // Memoize an expensive function by storing its results.
      _.memoize = function(func, hasher) {
        var memo = {};
        hasher || (hasher = _.identity);
        return function() {
          var key = hasher.apply(this, arguments);
          return _.has(memo, key) ? memo[key] : (memo[key] = func.apply(this, arguments));
        };
      };

      // Delays a function for the given number of milliseconds, and then calls
      // it with the arguments supplied.
      _.delay = function(func, wait) {
        var args = slice.call(arguments, 2);
        return setTimeout(function(){ return func.apply(null, args); }, wait);
      };

      // Defers a function, scheduling it to run after the current call stack has
      // cleared.
      _.defer = function(func) {
        return _.delay.apply(_, [func, 1].concat(slice.call(arguments, 1)));
      };

      // Returns a function, that, when invoked, will only be triggered at most once
      // during a given window of time.
      _.throttle = function(func, wait) {
        var context, args, timeout, throttling, more, result;
        var whenDone = _.debounce(function(){ more = throttling = false; }, wait);
        return function() {
          context = this; args = arguments;
          var later = function() {
            timeout = null;
            if (more) func.apply(context, args);
            whenDone();
          };
          if (!timeout) timeout = setTimeout(later, wait);
          if (throttling) {
            more = true;
          } else {
            result = func.apply(context, args);
          }
          whenDone();
          throttling = true;
          return result;
        };
      };

      // Returns a function, that, as long as it continues to be invoked, will not
      // be triggered. The function will be called after it stops being called for
      // N milliseconds. If `immediate` is passed, trigger the function on the
      // leading edge, instead of the trailing.
      _.debounce = function(func, wait, immediate) {
        var timeout;
        return function() {
          var context = this, args = arguments;
          var later = function() {
            timeout = null;
            if (!immediate) func.apply(context, args);
          };
          if (immediate && !timeout) func.apply(context, args);
          clearTimeout(timeout);
          timeout = setTimeout(later, wait);
        };
      };

      // Returns a function that will be executed at most one time, no matter how
      // often you call it. Useful for lazy initialization.
      _.once = function(func) {
        var ran = false, memo;
        return function() {
          if (ran) return memo;
          ran = true;
          return memo = func.apply(this, arguments);
        };
      };

      // Returns the first function passed as an argument to the second,
      // allowing you to adjust arguments, run code before and after, and
      // conditionally execute the original function.
      _.wrap = function(func, wrapper) {
        return function() {
          var args = [func].concat(slice.call(arguments, 0));
          return wrapper.apply(this, args);
        };
      };

      // Returns a function that is the composition of a list of functions, each
      // consuming the return value of the function that follows.
      _.compose = function() {
        var funcs = arguments;
        return function() {
          var args = arguments;
          for (var i = funcs.length - 1; i >= 0; i--) {
            args = [funcs[i].apply(this, args)];
          }
          return args[0];
        };
      };

      // Returns a function that will only be executed after being called N times.
      _.after = function(times, func) {
        if (times <= 0) return func();
        return function() {
          if (--times < 1) { return func.apply(this, arguments); }
        };
      };

      // Object Functions
      // ----------------

      // Retrieve the names of an object's properties.
      // Delegates to **ECMAScript 5**'s native `Object.keys`
      _.keys = nativeKeys || function(obj) {
        if (obj !== Object(obj)) throw new TypeError('Invalid object');
        var keys = [];
        for (var key in obj) if (_.has(obj, key)) keys[keys.length] = key;
        return keys;
      };

      // Retrieve the values of an object's properties.
      _.values = function(obj) {
        return _.map(obj, _.identity);
      };

      // Return a sorted list of the function names available on the object.
      // Aliased as `methods`
      _.functions = _.methods = function(obj) {
        var names = [];
        for (var key in obj) {
          if (_.isFunction(obj[key])) names.push(key);
        }
        return names.sort();
      };

      // Extend a given object with all the properties in passed-in object(s).
      _.extend = function(obj) {
        each(slice.call(arguments, 1), function(source) {
          for (var prop in source) {
            obj[prop] = source[prop];
          }
        });
        return obj;
      };

      // Return a copy of the object only containing the whitelisted properties.
      _.pick = function(obj) {
        var result = {};
        each(_.flatten(slice.call(arguments, 1)), function(key) {
          if (key in obj) result[key] = obj[key];
        });
        return result;
      };

      // Fill in a given object with default properties.
      _.defaults = function(obj) {
        each(slice.call(arguments, 1), function(source) {
          for (var prop in source) {
            if (obj[prop] == null) obj[prop] = source[prop];
          }
        });
        return obj;
      };

      // Create a (shallow-cloned) duplicate of an object.
      _.clone = function(obj) {
        if (!_.isObject(obj)) return obj;
        return _.isArray(obj) ? obj.slice() : _.extend({}, obj);
      };

      // Invokes interceptor with the obj, and then returns obj.
      // The primary purpose of this method is to "tap into" a method chain, in
      // order to perform operations on intermediate results within the chain.
      _.tap = function(obj, interceptor) {
        interceptor(obj);
        return obj;
      };

      // Internal recursive comparison function.
      function eq(a, b, stack) {
        // Identical objects are equal. `0 === -0`, but they aren't identical.
        // See the Harmony `egal` proposal: http://wiki.ecmascript.org/doku.php?id=harmony:egal.
        if (a === b) return a !== 0 || 1 / a == 1 / b;
        // A strict comparison is necessary because `null == undefined`.
        if (a == null || b == null) return a === b;
        // Unwrap any wrapped objects.
        if (a._chain) a = a._wrapped;
        if (b._chain) b = b._wrapped;
        // Invoke a custom `isEqual` method if one is provided.
        if (a.isEqual && _.isFunction(a.isEqual)) return a.isEqual(b);
        if (b.isEqual && _.isFunction(b.isEqual)) return b.isEqual(a);
        // Compare `[[Class]]` names.
        var className = toString.call(a);
        if (className != toString.call(b)) return false;
        switch (className) {
          // Strings, numbers, dates, and booleans are compared by value.
          case '[object String]':
            // Primitives and their corresponding object wrappers are equivalent; thus, `"5"` is
            // equivalent to `new String("5")`.
            return a == String(b);
          case '[object Number]':
            // `NaN`s are equivalent, but non-reflexive. An `egal` comparison is performed for
            // other numeric values.
            return a != +a ? b != +b : (a == 0 ? 1 / a == 1 / b : a == +b);
          case '[object Date]':
          case '[object Boolean]':
            // Coerce dates and booleans to numeric primitive values. Dates are compared by their
            // millisecond representations. Note that invalid dates with millisecond representations
            // of `NaN` are not equivalent.
            return +a == +b;
          // RegExps are compared by their source patterns and flags.
          case '[object RegExp]':
            return a.source == b.source &&
                   a.global == b.global &&
                   a.multiline == b.multiline &&
                   a.ignoreCase == b.ignoreCase;
        }
        if (typeof a != 'object' || typeof b != 'object') return false;
        // Assume equality for cyclic structures. The algorithm for detecting cyclic
        // structures is adapted from ES 5.1 section 15.12.3, abstract operation `JO`.
        var length = stack.length;
        while (length--) {
          // Linear search. Performance is inversely proportional to the number of
          // unique nested structures.
          if (stack[length] == a) return true;
        }
        // Add the first object to the stack of traversed objects.
        stack.push(a);
        var size = 0, result = true;
        // Recursively compare objects and arrays.
        if (className == '[object Array]') {
          // Compare array lengths to determine if a deep comparison is necessary.
          size = a.length;
          result = size == b.length;
          if (result) {
            // Deep compare the contents, ignoring non-numeric properties.
            while (size--) {
              // Ensure commutative equality for sparse arrays.
              if (!(result = size in a == size in b && eq(a[size], b[size], stack))) break;
            }
          }
        } else {
          // Objects with different constructors are not equivalent.
          if ('constructor' in a != 'constructor' in b || a.constructor != b.constructor) return false;
          // Deep compare objects.
          for (var key in a) {
            if (_.has(a, key)) {
              // Count the expected number of properties.
              size++;
              // Deep compare each member.
              if (!(result = _.has(b, key) && eq(a[key], b[key], stack))) break;
            }
          }
          // Ensure that both objects contain the same number of properties.
          if (result) {
            for (key in b) {
              if (_.has(b, key) && !(size--)) break;
            }
            result = !size;
          }
        }
        // Remove the first object from the stack of traversed objects.
        stack.pop();
        return result;
      }

      // Perform a deep comparison to check if two objects are equal.
      _.isEqual = function(a, b) {
        return eq(a, b, []);
      };

      // Is a given array, string, or object empty?
      // An "empty" object has no enumerable own-properties.
      _.isEmpty = function(obj) {
        if (obj == null) return true;
        if (_.isArray(obj) || _.isString(obj)) return obj.length === 0;
        for (var key in obj) if (_.has(obj, key)) return false;
        return true;
      };

      // Is a given value a DOM element?
      _.isElement = function(obj) {
        return !!(obj && obj.nodeType == 1);
      };

      // Is a given value an array?
      // Delegates to ECMA5's native Array.isArray
      _.isArray = nativeIsArray || function(obj) {
        return toString.call(obj) == '[object Array]';
      };

      // Is a given variable an object?
      _.isObject = function(obj) {
        return obj === Object(obj);
      };

      // Is a given variable an arguments object?
      _.isArguments = function(obj) {
        return toString.call(obj) == '[object Arguments]';
      };
      if (!_.isArguments(arguments)) {
        _.isArguments = function(obj) {
          return !!(obj && _.has(obj, 'callee'));
        };
      }

      // Is a given value a function?
      _.isFunction = function(obj) {
        return toString.call(obj) == '[object Function]';
      };

      // Is a given value a string?
      _.isString = function(obj) {
        return toString.call(obj) == '[object String]';
      };

      // Is a given value a number?
      _.isNumber = function(obj) {
        return toString.call(obj) == '[object Number]';
      };

      // Is a given object a finite number?
      _.isFinite = function(obj) {
        return _.isNumber(obj) && isFinite(obj);
      };

      // Is the given value `NaN`?
      _.isNaN = function(obj) {
        // `NaN` is the only value for which `===` is not reflexive.
        return obj !== obj;
      };

      // Is a given value a boolean?
      _.isBoolean = function(obj) {
        return obj === true || obj === false || toString.call(obj) == '[object Boolean]';
      };

      // Is a given value a date?
      _.isDate = function(obj) {
        return toString.call(obj) == '[object Date]';
      };

      // Is the given value a regular expression?
      _.isRegExp = function(obj) {
        return toString.call(obj) == '[object RegExp]';
      };

      // Is a given value equal to null?
      _.isNull = function(obj) {
        return obj === null;
      };

      // Is a given variable undefined?
      _.isUndefined = function(obj) {
        return obj === void 0;
      };

      // Has own property?
      _.has = function(obj, key) {
        return hasOwnProperty.call(obj, key);
      };

      // Utility Functions
      // -----------------

      // Run Underscore.js in *noConflict* mode, returning the `_` variable to its
      // previous owner. Returns a reference to the Underscore object.
      _.noConflict = function() {
        root._ = previousUnderscore;
        return this;
      };

      // Keep the identity function around for default iterators.
      _.identity = function(value) {
        return value;
      };

      // Run a function **n** times.
      _.times = function (n, iterator, context) {
        for (var i = 0; i < n; i++) iterator.call(context, i);
      };

      // Escape a string for HTML interpolation.
      _.escape = function(string) {
        return (''+string).replace(/&/g, '&amp;').replace(/</g, '&lt;').replace(/>/g, '&gt;').replace(/"/g, '&quot;').replace(/'/g, '&#x27;').replace(/\//g,'&#x2F;');
      };

      // If the value of the named property is a function then invoke it;
      // otherwise, return it.
      _.result = function(object, property) {
        if (object == null) return null;
        var value = object[property];
        return _.isFunction(value) ? value.call(object) : value;
      };

      // Add your own custom functions to the Underscore object, ensuring that
      // they're correctly added to the OOP wrapper as well.
      _.mixin = function(obj) {
        each(_.functions(obj), function(name){
          addToWrapper(name, _[name] = obj[name]);
        });
      };

      // Generate a unique integer id (unique within the entire client session).
      // Useful for temporary DOM ids.
      var idCounter = 0;
      _.uniqueId = function(prefix) {
        var id = idCounter++;
        return prefix ? prefix + id : id;
      };

      // By default, Underscore uses ERB-style template delimiters, change the
      // following template settings to use alternative delimiters.
      _.templateSettings = {
        evaluate    : /<%([\s\S]+?)%>/g,
        interpolate : /<%=([\s\S]+?)%>/g,
        escape      : /<%-([\s\S]+?)%>/g
      };

      // When customizing `templateSettings`, if you don't want to define an
      // interpolation, evaluation or escaping regex, we need one that is
      // guaranteed not to match.
      var noMatch = /.^/;

      // Certain characters need to be escaped so that they can be put into a
      // string literal.
      var escapes = {
        '\\': '\\',
        "'": "'",
        'r': '\r',
        'n': '\n',
        't': '\t',
        'u2028': '\u2028',
        'u2029': '\u2029'
      };

      for (var p in escapes) escapes[escapes[p]] = p;
      var escaper = /\\|'|\r|\n|\t|\u2028|\u2029/g;
      var unescaper = /\\(\\|'|r|n|t|u2028|u2029)/g;

      // Within an interpolation, evaluation, or escaping, remove HTML escaping
      // that had been previously added.
      var unescape = function(code) {
        return code.replace(unescaper, function(match, escape) {
          return escapes[escape];
        });
      };

      // JavaScript micro-templating, similar to John Resig's implementation.
      // Underscore templating handles arbitrary delimiters, preserves whitespace,
      // and correctly escapes quotes within interpolated code.
      _.template = function(text, data, settings) {
        settings = _.defaults(settings || {}, _.templateSettings);

        // Compile the template source, taking care to escape characters that
        // cannot be included in a string literal and then unescape them in code
        // blocks.
        var source = "__p+='" + text
          .replace(escaper, function(match) {
            return '\\' + escapes[match];
          })
          .replace(settings.escape || noMatch, function(match, code) {
            return "'+\n_.escape(" + unescape(code) + ")+\n'";
          })
          .replace(settings.interpolate || noMatch, function(match, code) {
            return "'+\n(" + unescape(code) + ")+\n'";
          })
          .replace(settings.evaluate || noMatch, function(match, code) {
            return "';\n" + unescape(code) + "\n;__p+='";
          }) + "';\n";

        // If a variable is not specified, place data values in local scope.
        if (!settings.variable) source = 'with(obj||{}){\n' + source + '}\n';

        source = "var __p='';" +
          "var print=function(){__p+=Array.prototype.join.call(arguments, '')};\n" +
          source + "return __p;\n";

        var render = new Function(settings.variable || 'obj', '_', source);
        if (data) return render(data, _);
        var template = function(data) {
          return render.call(this, data, _);
        };

        // Provide the compiled function source as a convenience for build time
        // precompilation.
        template.source = 'function(' + (settings.variable || 'obj') + '){\n' +
          source + '}';

        return template;
      };

      // Add a "chain" function, which will delegate to the wrapper.
      _.chain = function(obj) {
        return _(obj).chain();
      };

      // The OOP Wrapper
      // ---------------

      // If Underscore is called as a function, it returns a wrapped object that
      // can be used OO-style. This wrapper holds altered versions of all the
      // underscore functions. Wrapped objects may be chained.
      var wrapper = function(obj) { this._wrapped = obj; };

      // Expose `wrapper.prototype` as `_.prototype`
      _.prototype = wrapper.prototype;

      // Helper function to continue chaining intermediate results.
      var result = function(obj, chain) {
        return chain ? _(obj).chain() : obj;
      };

      // A method to easily add functions to the OOP wrapper.
      var addToWrapper = function(name, func) {
        wrapper.prototype[name] = function() {
          var args = slice.call(arguments);
          unshift.call(args, this._wrapped);
          return result(func.apply(_, args), this._chain);
        };
      };

      // Add all of the Underscore functions to the wrapper object.
      _.mixin(_);

      // Add all mutator Array functions to the wrapper.
      each(['pop', 'push', 'reverse', 'shift', 'sort', 'splice', 'unshift'], function(name) {
        var method = ArrayProto[name];
        wrapper.prototype[name] = function() {
          var wrapped = this._wrapped;
          method.apply(wrapped, arguments);
          var length = wrapped.length;
          if ((name == 'shift' || name == 'splice') && length === 0) delete wrapped[0];
          return result(wrapped, this._chain);
        };
      });

      // Add all accessor Array functions to the wrapper.
      each(['concat', 'join', 'slice'], function(name) {
        var method = ArrayProto[name];
        wrapper.prototype[name] = function() {
          return result(method.apply(this._wrapped, arguments), this._chain);
        };
      });

      // Start chaining a wrapped Underscore object.
      wrapper.prototype.chain = function() {
        this._chain = true;
        return this;
      };

      // Extracts the result from a wrapped and chained object.
      wrapper.prototype.value = function() {
        return this._wrapped;
      };

    }).call(this);

    });