text: // Copyright 2006 The Closure Library Authors. All Rights Reserved.
  //
  // Licensed 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.
  
  /**
   * @fileoverview Utilities for manipulating arrays.
   *
   * @author arv@google.com (Erik Arvidsson)
   */
  
  
  goog.provide('goog.array');
  goog.provide('goog.array.ArrayLike');
  
  goog.require('goog.asserts');
  
  
  /**
   * @define {boolean} NATIVE_ARRAY_PROTOTYPES indicates whether the code should
   * rely on Array.prototype functions, if available.
   *
   * The Array.prototype functions can be defined by external libraries like
   * Prototype and setting this flag to false forces closure to use its own
   * goog.array implementation.
   *
   * If your javascript can be loaded by a third party site and you are wary about
   * relying on the prototype functions, specify
   * "--define goog.NATIVE_ARRAY_PROTOTYPES=false" to the JSCompiler.
   *
   * Setting goog.TRUSTED_SITE to false will automatically set
   * NATIVE_ARRAY_PROTOTYPES to false.
   */
  goog.define('goog.NATIVE_ARRAY_PROTOTYPES', goog.TRUSTED_SITE);
  
  
  /**
   * @define {boolean} If true, JSCompiler will use the native implementation of
   * array functions where appropriate (e.g., {@code Array#filter}) and remove the
   * unused pure JS implementation.
   */
  goog.define('goog.array.ASSUME_NATIVE_FUNCTIONS', false);
  
  
  /**
   * @typedef {Array|NodeList|Arguments|{length: number}}
   */
  goog.array.ArrayLike;
  
  
  /**
   * Returns the last element in an array without removing it.
   * Same as goog.array.last.
   * @param {Array<T>|goog.array.ArrayLike} array The array.
   * @return {T} Last item in array.
   * @template T
   */
  goog.array.peek = function(array) {
    return array[array.length - 1];
  };
  
  
  /**
   * Returns the last element in an array without removing it.
   * Same as goog.array.peek.
   * @param {Array<T>|goog.array.ArrayLike} array The array.
   * @return {T} Last item in array.
   * @template T
   */
  goog.array.last = goog.array.peek;
  
  
  /**
   * Reference to the original {@code Array.prototype}.
   * @private
   */
  goog.array.ARRAY_PROTOTYPE_ = Array.prototype;
  
  
  // NOTE(arv): Since most of the array functions are generic it allows you to
  // pass an array-like object. Strings have a length and are considered array-
  // like. However, the 'in' operator does not work on strings so we cannot just
  // use the array path even if the browser supports indexing into strings. We
  // therefore end up splitting the string.
  
  
  /**
   * Returns the index of the first element of an array with a specified value, or
   * -1 if the element is not present in the array.
   *
   * See {@link http://tinyurl.com/developer-mozilla-org-array-indexof}
   *
   * @param {Array<T>|goog.array.ArrayLike} arr The array to be searched.
   * @param {T} obj The object for which we are searching.
   * @param {number=} opt_fromIndex The index at which to start the search. If
   *     omitted the search starts at index 0.
   * @return {number} The index of the first matching array element.
   * @template T
   */
  goog.array.indexOf = goog.NATIVE_ARRAY_PROTOTYPES &&
                       (goog.array.ASSUME_NATIVE_FUNCTIONS ||
                        goog.array.ARRAY_PROTOTYPE_.indexOf) ?
      function(arr, obj, opt_fromIndex) {
        goog.asserts.assert(arr.length != null);
  
        return goog.array.ARRAY_PROTOTYPE_.indexOf.call(arr, obj, opt_fromIndex);
      } :
      function(arr, obj, opt_fromIndex) {
        var fromIndex = opt_fromIndex == null ?
            0 : (opt_fromIndex < 0 ?
                 Math.max(0, arr.length + opt_fromIndex) : opt_fromIndex);
  
        if (goog.isString(arr)) {
          // Array.prototype.indexOf uses === so only strings should be found.
          if (!goog.isString(obj) || obj.length != 1) {
            return -1;
          }
          return arr.indexOf(obj, fromIndex);
        }
  
        for (var i = fromIndex; i < arr.length; i++) {
          if (i in arr && arr[i] === obj)
            return i;
        }
        return -1;
      };
  
  
  /**
   * Returns the index of the last element of an array with a specified value, or
   * -1 if the element is not present in the array.
   *
   * See {@link http://tinyurl.com/developer-mozilla-org-array-lastindexof}
   *
   * @param {!Array<T>|!goog.array.ArrayLike} arr The array to be searched.
   * @param {T} obj The object for which we are searching.
   * @param {?number=} opt_fromIndex The index at which to start the search. If
   *     omitted the search starts at the end of the array.
   * @return {number} The index of the last matching array element.
   * @template T
   */
  goog.array.lastIndexOf = goog.NATIVE_ARRAY_PROTOTYPES &&
                           (goog.array.ASSUME_NATIVE_FUNCTIONS ||
                            goog.array.ARRAY_PROTOTYPE_.lastIndexOf) ?
      function(arr, obj, opt_fromIndex) {
        goog.asserts.assert(arr.length != null);
  
        // Firefox treats undefined and null as 0 in the fromIndex argument which
        // leads it to always return -1
        var fromIndex = opt_fromIndex == null ? arr.length - 1 : opt_fromIndex;
        return goog.array.ARRAY_PROTOTYPE_.lastIndexOf.call(arr, obj, fromIndex);
      } :
      function(arr, obj, opt_fromIndex) {
        var fromIndex = opt_fromIndex == null ? arr.length - 1 : opt_fromIndex;
  
        if (fromIndex < 0) {
          fromIndex = Math.max(0, arr.length + fromIndex);
        }
  
        if (goog.isString(arr)) {
          // Array.prototype.lastIndexOf uses === so only strings should be found.
          if (!goog.isString(obj) || obj.length != 1) {
            return -1;
          }
          return arr.lastIndexOf(obj, fromIndex);
        }
  
        for (var i = fromIndex; i >= 0; i--) {
          if (i in arr && arr[i] === obj)
            return i;
        }
        return -1;
      };
  
  
  /**
   * Calls a function for each element in an array. Skips holes in the array.
   * See {@link http://tinyurl.com/developer-mozilla-org-array-foreach}
   *
   * @param {Array<T>|goog.array.ArrayLike} arr Array or array like object over
   *     which to iterate.
   * @param {?function(this: S, T, number, ?): ?} f The function to call for every
   *     element. This function takes 3 arguments (the element, the index and the
   *     array). The return value is ignored.
   * @param {S=} opt_obj The object to be used as the value of 'this' within f.
   * @template T,S
   */
  goog.array.forEach = goog.NATIVE_ARRAY_PROTOTYPES &&
                       (goog.array.ASSUME_NATIVE_FUNCTIONS ||
                        goog.array.ARRAY_PROTOTYPE_.forEach) ?
      function(arr, f, opt_obj) {
        goog.asserts.assert(arr.length != null);
  
        goog.array.ARRAY_PROTOTYPE_.forEach.call(arr, f, opt_obj);
      } :
      function(arr, f, opt_obj) {
        var l = arr.length;  // must be fixed during loop... see docs
        var arr2 = goog.isString(arr) ? arr.split('') : arr;
        for (var i = 0; i < l; i++) {
          if (i in arr2) {
            f.call(opt_obj, arr2[i], i, arr);
          }
        }
      };
  
  
  /**
   * Calls a function for each element in an array, starting from the last
   * element rather than the first.
   *
   * @param {Array<T>|goog.array.ArrayLike} arr Array or array
   *     like object over which to iterate.
   * @param {?function(this: S, T, number, ?): ?} f The function to call for every
   *     element. This function
   *     takes 3 arguments (the element, the index and the array). The return
   *     value is ignored.
   * @param {S=} opt_obj The object to be used as the value of 'this'
   *     within f.
   * @template T,S
   */
  goog.array.forEachRight = function(arr, f, opt_obj) {
    var l = arr.length;  // must be fixed during loop... see docs
    var arr2 = goog.isString(arr) ? arr.split('') : arr;
    for (var i = l - 1; i >= 0; --i) {
      if (i in arr2) {
        f.call(opt_obj, arr2[i], i, arr);
      }
    }
  };
  
  
  /**
   * Calls a function for each element in an array, and if the function returns
   * true adds the element to a new array.
   *
   * See {@link http://tinyurl.com/developer-mozilla-org-array-filter}
   *
   * @param {Array<T>|goog.array.ArrayLike} arr Array or array
   *     like object over which to iterate.
   * @param {?function(this:S, T, number, ?):boolean} f The function to call for
   *     every element. This function
   *     takes 3 arguments (the element, the index and the array) and must
   *     return a Boolean. If the return value is true the element is added to the
   *     result array. If it is false the element is not included.
   * @param {S=} opt_obj The object to be used as the value of 'this'
   *     within f.
   * @return {!Array<T>} a new array in which only elements that passed the test
   *     are present.
   * @template T,S
   */
  goog.array.filter = goog.NATIVE_ARRAY_PROTOTYPES &&
                      (goog.array.ASSUME_NATIVE_FUNCTIONS ||
                       goog.array.ARRAY_PROTOTYPE_.filter) ?
      function(arr, f, opt_obj) {
        goog.asserts.assert(arr.length != null);
  
        return goog.array.ARRAY_PROTOTYPE_.filter.call(arr, f, opt_obj);
      } :
      function(arr, f, opt_obj) {
        var l = arr.length;  // must be fixed during loop... see docs
        var res = [];
        var resLength = 0;
        var arr2 = goog.isString(arr) ? arr.split('') : arr;
        for (var i = 0; i < l; i++) {
          if (i in arr2) {
            var val = arr2[i];  // in case f mutates arr2
            if (f.call(opt_obj, val, i, arr)) {
              res[resLength++] = val;
            }
          }
        }
        return res;
      };
  
  
  /**
   * Calls a function for each element in an array and inserts the result into a
   * new array.
   *
   * See {@link http://tinyurl.com/developer-mozilla-org-array-map}
   *
   * @param {Array<VALUE>|goog.array.ArrayLike} arr Array or array like object
   *     over which to iterate.
   * @param {function(this:THIS, VALUE, number, ?): RESULT} f The function to call
   *     for every element. This function takes 3 arguments (the element,
   *     the index and the array) and should return something. The result will be
   *     inserted into a new array.
   * @param {THIS=} opt_obj The object to be used as the value of 'this' within f.
   * @return {!Array<RESULT>} a new array with the results from f.
   * @template THIS, VALUE, RESULT
   */
  goog.array.map = goog.NATIVE_ARRAY_PROTOTYPES &&
                   (goog.array.ASSUME_NATIVE_FUNCTIONS ||
                    goog.array.ARRAY_PROTOTYPE_.map) ?
      function(arr, f, opt_obj) {
        goog.asserts.assert(arr.length != null);
  
        return goog.array.ARRAY_PROTOTYPE_.map.call(arr, f, opt_obj);
      } :
      function(arr, f, opt_obj) {
        var l = arr.length;  // must be fixed during loop... see docs
        var res = new Array(l);
        var arr2 = goog.isString(arr) ? arr.split('') : arr;
        for (var i = 0; i < l; i++) {
          if (i in arr2) {
            res[i] = f.call(opt_obj, arr2[i], i, arr);
          }
        }
        return res;
      };
  
  
  /**
   * Passes every element of an array into a function and accumulates the result.
   *
   * See {@link http://tinyurl.com/developer-mozilla-org-array-reduce}
   *
   * For example:
   * var a = [1, 2, 3, 4];
   * goog.array.reduce(a, function(r, v, i, arr) {return r + v;}, 0);
   * returns 10
   *
   * @param {Array<T>|goog.array.ArrayLike} arr Array or array
   *     like object over which to iterate.
   * @param {function(this:S, R, T, number, ?) : R} f The function to call for
   *     every element. This function
   *     takes 4 arguments (the function's previous result or the initial value,
   *     the value of the current array element, the current array index, and the
   *     array itself)
   *     function(previousValue, currentValue, index, array).
   * @param {?} val The initial value to pass into the function on the first call.
   * @param {S=} opt_obj  The object to be used as the value of 'this'
   *     within f.
   * @return {R} Result of evaluating f repeatedly across the values of the array.
   * @template T,S,R
   */
  goog.array.reduce = goog.NATIVE_ARRAY_PROTOTYPES &&
                      (goog.array.ASSUME_NATIVE_FUNCTIONS ||
                       goog.array.ARRAY_PROTOTYPE_.reduce) ?
      function(arr, f, val, opt_obj) {
        goog.asserts.assert(arr.length != null);
        var params = [];
        for(var i = 1, l = arguments.length; i < l; i++){
          params.push(arguments[i]);
        }
        if (opt_obj) {
          params[0] = goog.bind(f, opt_obj);
        }
        return goog.array.ARRAY_PROTOTYPE_.reduce.apply(arr, params);
      } :
      function(arr, f, val, opt_obj) {
        var rval = val;
        goog.array.forEach(arr, function(val, index) {
          rval = f.call(opt_obj, rval, val, index, arr);
        });
        return rval;
      };
  
  
  /**
   * Passes every element of an array into a function and accumulates the result,
   * starting from the last element and working towards the first.
   *
   * See {@link http://tinyurl.com/developer-mozilla-org-array-reduceright}
   *
   * For example:
   * var a = ['a', 'b', 'c'];
   * goog.array.reduceRight(a, function(r, v, i, arr) {return r + v;}, '');
   * returns 'cba'
   *
   * @param {Array<T>|goog.array.ArrayLike} arr Array or array
   *     like object over which to iterate.
   * @param {?function(this:S, R, T, number, ?) : R} f The function to call for
   *     every element. This function
   *     takes 4 arguments (the function's previous result or the initial value,
   *     the value of the current array element, the current array index, and the
   *     array itself)
   *     function(previousValue, currentValue, index, array).
   * @param {?} val The initial value to pass into the function on the first call.
   * @param {S=} opt_obj The object to be used as the value of 'this'
   *     within f.
   * @return {R} Object returned as a result of evaluating f repeatedly across the
   *     values of the array.
   * @template T,S,R
   */
  goog.array.reduceRight = goog.NATIVE_ARRAY_PROTOTYPES &&
                           (goog.array.ASSUME_NATIVE_FUNCTIONS ||
                            goog.array.ARRAY_PROTOTYPE_.reduceRight) ?
      function(arr, f, val, opt_obj) {
        goog.asserts.assert(arr.length != null);
        if (opt_obj) {
          f = goog.bind(f, opt_obj);
        }
        return goog.array.ARRAY_PROTOTYPE_.reduceRight.call(arr, f, val);
      } :
      function(arr, f, val, opt_obj) {
        var rval = val;
        goog.array.forEachRight(arr, function(val, index) {
          rval = f.call(opt_obj, rval, val, index, arr);
        });
        return rval;
      };
  
  
  /**
   * Calls f for each element of an array. If any call returns true, some()
   * returns true (without checking the remaining elements). If all calls
   * return false, some() returns false.
   *
   * See {@link http://tinyurl.com/developer-mozilla-org-array-some}
   *
   * @param {Array<T>|goog.array.ArrayLike} arr Array or array
   *     like object over which to iterate.
   * @param {?function(this:S, T, number, ?) : boolean} f The function to call for
   *     for every element. This function takes 3 arguments (the element, the
   *     index and the array) and should return a boolean.
   * @param {S=} opt_obj  The object to be used as the value of 'this'
   *     within f.
   * @return {boolean} true if any element passes the test.
   * @template T,S
   */
  goog.array.some = goog.NATIVE_ARRAY_PROTOTYPES &&
                    (goog.array.ASSUME_NATIVE_FUNCTIONS ||
                     goog.array.ARRAY_PROTOTYPE_.some) ?
      function(arr, f, opt_obj) {
        goog.asserts.assert(arr.length != null);
  
        return goog.array.ARRAY_PROTOTYPE_.some.call(arr, f, opt_obj);
      } :
      function(arr, f, opt_obj) {
        var l = arr.length;  // must be fixed during loop... see docs
        var arr2 = goog.isString(arr) ? arr.split('') : arr;
        for (var i = 0; i < l; i++) {
          if (i in arr2 && f.call(opt_obj, arr2[i], i, arr)) {
            return true;
          }
        }
        return false;
      };
  
  
  /**
   * Call f for each element of an array. If all calls return true, every()
   * returns true. If any call returns false, every() returns false and
   * does not continue to check the remaining elements.
   *
   * See {@link http://tinyurl.com/developer-mozilla-org-array-every}
   *
   * @param {Array<T>|goog.array.ArrayLike} arr Array or array
   *     like object over which to iterate.
   * @param {?function(this:S, T, number, ?) : boolean} f The function to call for
   *     for every element. This function takes 3 arguments (the element, the
   *     index and the array) and should return a boolean.
   * @param {S=} opt_obj The object to be used as the value of 'this'
   *     within f.
   * @return {boolean} false if any element fails the test.
   * @template T,S
   */
  goog.array.every = goog.NATIVE_ARRAY_PROTOTYPES &&
                     (goog.array.ASSUME_NATIVE_FUNCTIONS ||
                      goog.array.ARRAY_PROTOTYPE_.every) ?
      function(arr, f, opt_obj) {
        goog.asserts.assert(arr.length != null);
  
        return goog.array.ARRAY_PROTOTYPE_.every.call(arr, f, opt_obj);
      } :
      function(arr, f, opt_obj) {
        var l = arr.length;  // must be fixed during loop... see docs
        var arr2 = goog.isString(arr) ? arr.split('') : arr;
        for (var i = 0; i < l; i++) {
          if (i in arr2 && !f.call(opt_obj, arr2[i], i, arr)) {
            return false;
          }
        }
        return true;
      };
  
  
  /**
   * Counts the array elements that fulfill the predicate, i.e. for which the
   * callback function returns true. Skips holes in the array.
   *
   * @param {!(Array<T>|goog.array.ArrayLike)} arr Array or array like object
   *     over which to iterate.
   * @param {function(this: S, T, number, ?): boolean} f The function to call for
   *     every element. Takes 3 arguments (the element, the index and the array).
   * @param {S=} opt_obj The object to be used as the value of 'this' within f.
   * @return {number} The number of the matching elements.
   * @template T,S
   */
  goog.array.count = function(arr, f, opt_obj) {
    var count = 0;
    goog.array.forEach(arr, function(element, index, arr) {
      if (f.call(opt_obj, element, index, arr)) {
        ++count;
      }
    }, opt_obj);
    return count;
  };
  
  
  /**
   * Search an array for the first element that satisfies a given condition and
   * return that element.
   * @param {Array<T>|goog.array.ArrayLike} arr Array or array
   *     like object over which to iterate.
   * @param {?function(this:S, T, number, ?) : boolean} f The function to call
   *     for every element. This function takes 3 arguments (the element, the
   *     index and the array) and should return a boolean.
   * @param {S=} opt_obj An optional "this" context for the function.
   * @return {T|null} The first array element that passes the test, or null if no
   *     element is found.
   * @template T,S
   */
  goog.array.find = function(arr, f, opt_obj) {
    var i = goog.array.findIndex(arr, f, opt_obj);
    return i < 0 ? null : goog.isString(arr) ? arr.charAt(i) : arr[i];
  };
  
  
  /**
   * Search an array for the first element that satisfies a given condition and
   * return its index.
   * @param {Array<T>|goog.array.ArrayLike} arr Array or array
   *     like object over which to iterate.
   * @param {?function(this:S, T, number, ?) : boolean} f The function to call for
   *     every element. This function
   *     takes 3 arguments (the element, the index and the array) and should
   *     return a boolean.
   * @param {S=} opt_obj An optional "this" context for the function.
   * @return {number} The index of the first array element that passes the test,
   *     or -1 if no element is found.
   * @template T,S
   */
  goog.array.findIndex = function(arr, f, opt_obj) {
    var l = arr.length;  // must be fixed during loop... see docs
    var arr2 = goog.isString(arr) ? arr.split('') : arr;
    for (var i = 0; i < l; i++) {
      if (i in arr2 && f.call(opt_obj, arr2[i], i, arr)) {
        return i;
      }
    }
    return -1;
  };
  
  
  /**
   * Search an array (in reverse order) for the last element that satisfies a
   * given condition and return that element.
   * @param {Array<T>|goog.array.ArrayLike} arr Array or array
   *     like object over which to iterate.
   * @param {?function(this:S, T, number, ?) : boolean} f The function to call
   *     for every element. This function
   *     takes 3 arguments (the element, the index and the array) and should
   *     return a boolean.
   * @param {S=} opt_obj An optional "this" context for the function.
   * @return {T|null} The last array element that passes the test, or null if no
   *     element is found.
   * @template T,S
   */
  goog.array.findRight = function(arr, f, opt_obj) {
    var i = goog.array.findIndexRight(arr, f, opt_obj);
    return i < 0 ? null : goog.isString(arr) ? arr.charAt(i) : arr[i];
  };
  
  
  /**
   * Search an array (in reverse order) for the last element that satisfies a
   * given condition and return its index.
   * @param {Array<T>|goog.array.ArrayLike} arr Array or array
   *     like object over which to iterate.
   * @param {?function(this:S, T, number, ?) : boolean} f The function to call
   *     for every element. This function
   *     takes 3 arguments (the element, the index and the array) and should
   *     return a boolean.
   * @param {S=} opt_obj An optional "this" context for the function.
   * @return {number} The index of the last array element that passes the test,
   *     or -1 if no element is found.
   * @template T,S
   */
  goog.array.findIndexRight = function(arr, f, opt_obj) {
    var l = arr.length;  // must be fixed during loop... see docs
    var arr2 = goog.isString(arr) ? arr.split('') : arr;
    for (var i = l - 1; i >= 0; i--) {
      if (i in arr2 && f.call(opt_obj, arr2[i], i, arr)) {
        return i;
      }
    }
    return -1;
  };
  
  
  /**
   * Whether the array contains the given object.
   * @param {goog.array.ArrayLike} arr The array to test for the presence of the
   *     element.
   * @param {*} obj The object for which to test.
   * @return {boolean} true if obj is present.
   */
  goog.array.contains = function(arr, obj) {
    return goog.array.indexOf(arr, obj) >= 0;
  };
  
  
  /**
   * Whether the array is empty.
   * @param {goog.array.ArrayLike} arr The array to test.
   * @return {boolean} true if empty.
   */
  goog.array.isEmpty = function(arr) {
    return arr.length == 0;
  };
  
  
  /**
   * Clears the array.
   * @param {goog.array.ArrayLike} arr Array or array like object to clear.
   */
  goog.array.clear = function(arr) {
    // For non real arrays we don't have the magic length so we delete the
    // indices.
    if (!goog.isArray(arr)) {
      for (var i = arr.length - 1; i >= 0; i--) {
        delete arr[i];
      }
    }
    arr.length = 0;
  };
  
  
  /**
   * Pushes an item into an array, if it's not already in the array.
   * @param {Array<T>} arr Array into which to insert the item.
   * @param {T} obj Value to add.
   * @template T
   */
  goog.array.insert = function(arr, obj) {
    if (!goog.array.contains(arr, obj)) {
      arr.push(obj);
    }
  };
  
  
  /**
   * Inserts an object at the given index of the array.
   * @param {goog.array.ArrayLike} arr The array to modify.
   * @param {*} obj The object to insert.
   * @param {number=} opt_i The index at which to insert the object. If omitted,
   *      treated as 0. A negative index is counted from the end of the array.
   */
  goog.array.insertAt = function(arr, obj, opt_i) {
    goog.array.splice(arr, opt_i, 0, obj);
  };
  
  
  /**
   * Inserts at the given index of the array, all elements of another array.
   * @param {goog.array.ArrayLike} arr The array to modify.
   * @param {goog.array.ArrayLike} elementsToAdd The array of elements to add.
   * @param {number=} opt_i The index at which to insert the object. If omitted,
   *      treated as 0. A negative index is counted from the end of the array.
   */
  goog.array.insertArrayAt = function(arr, elementsToAdd, opt_i) {
    goog.partial(goog.array.splice, arr, opt_i, 0).apply(null, elementsToAdd);
  };
  
  
  /**
   * Inserts an object into an array before a specified object.
   * @param {Array<T>} arr The array to modify.
   * @param {T} obj The object to insert.
   * @param {T=} opt_obj2 The object before which obj should be inserted. If obj2
   *     is omitted or not found, obj is inserted at the end of the array.
   * @template T
   */
  goog.array.insertBefore = function(arr, obj, opt_obj2) {
    var i;
    if (arguments.length == 2 || (i = goog.array.indexOf(arr, opt_obj2)) < 0) {
      arr.push(obj);
    } else {
      goog.array.insertAt(arr, obj, i);
    }
  };
  
  
  /**
   * Removes the first occurrence of a particular value from an array.
   * @param {Array<T>|goog.array.ArrayLike} arr Array from which to remove
   *     value.
   * @param {T} obj Object to remove.
   * @return {boolean} True if an element was removed.
   * @template T
   */
  goog.array.remove = function(arr, obj) {
    var i = goog.array.indexOf(arr, obj);
    var rv;
    if ((rv = i >= 0)) {
      goog.array.removeAt(arr, i);
    }
    return rv;
  };
  
  
  /**
   * Removes from an array the element at index i
   * @param {goog.array.ArrayLike} arr Array or array like object from which to
   *     remove value.
   * @param {number} i The index to remove.
   * @return {boolean} True if an element was removed.
   */
  goog.array.removeAt = function(arr, i) {
    goog.asserts.assert(arr.length != null);
  
    // use generic form of splice
    // splice returns the removed items and if successful the length of that
    // will be 1
    return goog.array.ARRAY_PROTOTYPE_.splice.call(arr, i, 1).length == 1;
  };
  
  
  /**
   * Removes the first value that satisfies the given condition.
   * @param {Array<T>|goog.array.ArrayLike} arr Array or array
   *     like object over which to iterate.
   * @param {?function(this:S, T, number, ?) : boolean} f The function to call
   *     for every element. This function
   *     takes 3 arguments (the element, the index and the array) and should
   *     return a boolean.
   * @param {S=} opt_obj An optional "this" context for the function.
   * @return {boolean} True if an element was removed.
   * @template T,S
   */
  goog.array.removeIf = function(arr, f, opt_obj) {
    var i = goog.array.findIndex(arr, f, opt_obj);
    if (i >= 0) {
      goog.array.removeAt(arr, i);
      return true;
    }
    return false;
  };
  
  
  /**
   * Removes all values that satisfy the given condition.
   * @param {Array<T>|goog.array.ArrayLike} arr Array or array
   *     like object over which to iterate.
   * @param {?function(this:S, T, number, ?) : boolean} f The function to call
   *     for every element. This function
   *     takes 3 arguments (the element, the index and the array) and should
   *     return a boolean.
   * @param {S=} opt_obj An optional "this" context for the function.
   * @return {number} The number of items removed
   * @template T,S
   */
  goog.array.removeAllIf = function(arr, f, opt_obj) {
    var removedCount = 0;
    goog.array.forEachRight(arr, function(val, index) {
      if (f.call(opt_obj, val, index, arr)) {
        if (goog.array.removeAt(arr, index)) {
          removedCount++;
        }
      }
    });
    return removedCount;
  };
  
  
  /**
   * Returns a new array that is the result of joining the arguments.  If arrays
   * are passed then their items are added, however, if non-arrays are passed they
   * will be added to the return array as is.
   *
   * Note that ArrayLike objects will be added as is, rather than having their
   * items added.
   *
   * goog.array.concat([1, 2], [3, 4]) -> [1, 2, 3, 4]
   * goog.array.concat(0, [1, 2]) -> [0, 1, 2]
   * goog.array.concat([1, 2], null) -> [1, 2, null]
   *
   * There is bug in all current versions of IE (6, 7 and 8) where arrays created
   * in an iframe become corrupted soon (not immediately) after the iframe is
   * destroyed. This is common if loading data via goog.net.IframeIo, for example.
   * This corruption only affects the concat method which will start throwing
   * Catastrophic Errors (#-2147418113).
   *
   * See http://endoflow.com/scratch/corrupted-arrays.html for a test case.
   *
   * Internally goog.array should use this, so that all methods will continue to
   * work on these broken array objects.
   *
   * @param {...*} var_args Items to concatenate.  Arrays will have each item
   *     added, while primitives and objects will be added as is.
   * @return {!Array<?>} The new resultant array.
   */
  goog.array.concat = function(var_args) {
    return goog.array.ARRAY_PROTOTYPE_.concat.apply(
        goog.array.ARRAY_PROTOTYPE_, arguments);
  };
  
  
  /**
   * Returns a new array that contains the contents of all the arrays passed.
   * @param {...!Array<T>} var_args
   * @return {!Array<T>}
   * @template T
   */
  goog.array.join = function(var_args) {
    return goog.array.ARRAY_PROTOTYPE_.concat.apply(
        goog.array.ARRAY_PROTOTYPE_, arguments);
  };
  
  
  /**
   * Converts an object to an array.
   * @param {Array<T>|goog.array.ArrayLike} object  The object to convert to an
   *     array.
   * @return {!Array<T>} The object converted into an array. If object has a
   *     length property, every property indexed with a non-negative number
   *     less than length will be included in the result. If object does not
   *     have a length property, an empty array will be returned.
   * @template T
   */
  goog.array.toArray = function(object) {
    var length = object.length;
  
    // If length is not a number the following it false. This case is kept for
    // backwards compatibility since there are callers that pass objects that are
    // not array like.
    if (length > 0) {
      var rv = new Array(length);
      for (var i = 0; i < length; i++) {
        rv[i] = object[i];
      }
      return rv;
    }
    return [];
  };
  
  
  /**
   * Does a shallow copy of an array.
   * @param {Array<T>|goog.array.ArrayLike} arr  Array or array-like object to
   *     clone.
   * @return {!Array<T>} Clone of the input array.
   * @template T
   */
  goog.array.clone = goog.array.toArray;
  
  
  /**
   * Extends an array with another array, element, or "array like" object.
   * This function operates 'in-place', it does not create a new Array.
   *
   * Example:
   * var a = [];
   * goog.array.extend(a, [0, 1]);
   * a; // [0, 1]
   * goog.array.extend(a, 2);
   * a; // [0, 1, 2]
   *
   * @param {Array<VALUE>} arr1  The array to modify.
   * @param {...(Array<VALUE>|VALUE)} var_args The elements or arrays of elements
   *     to add to arr1.
   * @template VALUE
   */
  goog.array.extend = function(arr1, var_args) {
    for (var i = 1; i < arguments.length; i++) {
      var arr2 = arguments[i];
      if (goog.isArrayLike(arr2)) {
        var len1 = arr1.length || 0;
        var len2 = arr2.length || 0;
        arr1.length = len1 + len2;
        for (var j = 0; j < len2; j++) {
          arr1[len1 + j] = arr2[j];
        }
      } else {
        arr1.push(arr2);
      }
    }
  };
  
  
  /**
   * Adds or removes elements from an array. This is a generic version of Array
   * splice. This means that it might work on other objects similar to arrays,
   * such as the arguments object.
   *
   * @param {Array<T>|goog.array.ArrayLike} arr The array to modify.
   * @param {number|undefined} index The index at which to start changing the
   *     array. If not defined, treated as 0.
   * @param {number} howMany How many elements to remove (0 means no removal. A
   *     value below 0 is treated as zero and so is any other non number. Numbers
   *     are floored).
   * @param {...T} var_args Optional, additional elements to insert into the
   *     array.
   * @return {!Array<T>} the removed elements.
   * @template T
   */
  goog.array.splice = function(arr, index, howMany, var_args) {
    goog.asserts.assert(arr.length != null);
  
    return goog.array.ARRAY_PROTOTYPE_.splice.apply(
        arr, goog.array.slice(arguments, 1));
  };
  
  
  /**
   * Returns a new array from a segment of an array. This is a generic version of
   * Array slice. This means that it might work on other objects similar to
   * arrays, such as the arguments object.
   *
   * @param {Array<T>|goog.array.ArrayLike} arr The array from
   * which to copy a segment.
   * @param {number} start The index of the first element to copy.
   * @param {number=} opt_end The index after the last element to copy.
   * @return {!Array<T>} A new array containing the specified segment of the
   *     original array.
   * @template T
   */
  goog.array.slice = function(arr, start, opt_end) {
    goog.asserts.assert(arr.length != null);
  
    // passing 1 arg to slice is not the same as passing 2 where the second is
    // null or undefined (in that case the second argument is treated as 0).
    // we could use slice on the arguments object and then use apply instead of
    // testing the length
    if (arguments.length <= 2) {
      return goog.array.ARRAY_PROTOTYPE_.slice.call(arr, start);
    } else {
      return goog.array.ARRAY_PROTOTYPE_.slice.call(arr, start, opt_end);
    }
  };
  
  
  /**
   * Removes all duplicates from an array (retaining only the first
   * occurrence of each array element).  This function modifies the
   * array in place and doesn't change the order of the non-duplicate items.
   *
   * For objects, duplicates are identified as having the same unique ID as
   * defined by {@link goog.getUid}.
   *
   * Alternatively you can specify a custom hash function that returns a unique
   * value for each item in the array it should consider unique.
   *
   * Runtime: N,
   * Worstcase space: 2N (no dupes)
   *
   * @param {Array<T>|goog.array.ArrayLike} arr The array from which to remove
   *     duplicates.
   * @param {Array=} opt_rv An optional array in which to return the results,
   *     instead of performing the removal inplace.  If specified, the original
   *     array will remain unchanged.
   * @param {function(T):string=} opt_hashFn An optional function to use to
   *     apply to every item in the array. This function should return a unique
   *     value for each item in the array it should consider unique.
   * @template T
   */
  goog.array.removeDuplicates = function(arr, opt_rv, opt_hashFn) {
    var returnArray = opt_rv || arr;
    var defaultHashFn = function(item) {
      // Prefix each type with a single character representing the type to
      // prevent conflicting keys (e.g. true and 'true').
      return goog.isObject(current) ? 'o' + goog.getUid(current) :
          (typeof current).charAt(0) + current;
    };
    var hashFn = opt_hashFn || defaultHashFn;
  
    var seen = {}, cursorInsert = 0, cursorRead = 0;
    while (cursorRead < arr.length) {
      var current = arr[cursorRead++];
      var key = hashFn(current);
      if (!Object.prototype.hasOwnProperty.call(seen, key)) {
        seen[key] = true;
        returnArray[cursorInsert++] = current;
      }
    }
    returnArray.length = cursorInsert;
  };
  
  
  /**
   * Searches the specified array for the specified target using the binary
   * search algorithm.  If no opt_compareFn is specified, elements are compared
   * using <code>goog.array.defaultCompare</code>, which compares the elements
   * using the built in < and > operators.  This will produce the expected
   * behavior for homogeneous arrays of String(s) and Number(s). The array
   * specified <b>must</b> be sorted in ascending order (as defined by the
   * comparison function).  If the array is not sorted, results are undefined.
   * If the array contains multiple instances of the specified target value, any
   * of these instances may be found.
   *
   * Runtime: O(log n)
   *
   * @param {Array<VALUE>|goog.array.ArrayLike} arr The array to be searched.
   * @param {TARGET} target The sought value.
   * @param {function(TARGET, VALUE): number=} opt_compareFn Optional comparison
   *     function by which the array is ordered. Should take 2 arguments to
   *     compare, and return a negative number, zero, or a positive number
   *     depending on whether the first argument is less than, equal to, or
   *     greater than the second.
   * @return {number} Lowest index of the target value if found, otherwise
   *     (-(insertion point) - 1). The insertion point is where the value should
   *     be inserted into arr to preserve the sorted property.  Return value >= 0
   *     iff target is found.
   * @template TARGET, VALUE
   */
  goog.array.binarySearch = function(arr, target, opt_compareFn) {
    return goog.array.binarySearch_(arr,
        opt_compareFn || goog.array.defaultCompare, false /* isEvaluator */,
        target);
  };
  
  
  /**
   * Selects an index in the specified array using the binary search algorithm.
   * The evaluator receives an element and determines whether the desired index
   * is before, at, or after it.  The evaluator must be consistent (formally,
   * goog.array.map(goog.array.map(arr, evaluator, opt_obj), goog.math.sign)
   * must be monotonically non-increasing).
   *
   * Runtime: O(log n)
   *
   * @param {Array<VALUE>|goog.array.ArrayLike} arr The array to be searched.
   * @param {function(this:THIS, VALUE, number, ?): number} evaluator
   *     Evaluator function that receives 3 arguments (the element, the index and
   *     the array). Should return a negative number, zero, or a positive number
   *     depending on whether the desired index is before, at, or after the
   *     element passed to it.
   * @param {THIS=} opt_obj The object to be used as the value of 'this'
   *     within evaluator.
   * @return {number} Index of the leftmost element matched by the evaluator, if
   *     such exists; otherwise (-(insertion point) - 1). The insertion point is
   *     the index of the first element for which the evaluator returns negative,
   *     or arr.length if no such element exists. The return value is non-negative
   *     iff a match is found.
   * @template THIS, VALUE
   */
  goog.array.binarySelect = function(arr, evaluator, opt_obj) {
    return goog.array.binarySearch_(arr, evaluator, true /* isEvaluator */,
        undefined /* opt_target */, opt_obj);
  };
  
  
  /**
   * Implementation of a binary search algorithm which knows how to use both
   * comparison functions and evaluators. If an evaluator is provided, will call
   * the evaluator with the given optional data object, conforming to the
   * interface defined in binarySelect. Otherwise, if a comparison function is
   * provided, will call the comparison function against the given data object.
   *
   * This implementation purposefully does not use goog.bind or goog.partial for
   * performance reasons.
   *
   * Runtime: O(log n)
   *
   * @param {Array<VALUE>|goog.array.ArrayLike} arr The array to be searched.
   * @param {function(TARGET, VALUE): number|
   *         function(this:THIS, VALUE, number, ?): number} compareFn Either an
   *     evaluator or a comparison function, as defined by binarySearch
   *     and binarySelect above.
   * @param {boolean} isEvaluator Whether the function is an evaluator or a
   *     comparison function.
   * @param {TARGET=} opt_target If the function is a comparison function, then
   *     this is the target to binary search for.
   * @param {THIS=} opt_selfObj If the function is an evaluator, this is an
    *    optional this object for the evaluator.
   * @return {number} Lowest index of the target value if found, otherwise
   *     (-(insertion point) - 1). The insertion point is where the value should
   *     be inserted into arr to preserve the sorted property.  Return value >= 0
   *     iff target is found.
   * @template THIS, VALUE, TARGET
   * @private
   */
  goog.array.binarySearch_ = function(arr, compareFn, isEvaluator, opt_target,
      opt_selfObj) {
    var left = 0;  // inclusive
    var right = arr.length;  // exclusive
    var found;
    while (left < right) {
      var middle = (left + right) >> 1;
      var compareResult;
      if (isEvaluator) {
        compareResult = compareFn.call(opt_selfObj, arr[middle], middle, arr);
      } else {
        compareResult = compareFn(opt_target, arr[middle]);
      }
      if (compareResult > 0) {
        left = middle + 1;
      } else {
        right = middle;
        // We are looking for the lowest index so we can't return immediately.
        found = !compareResult;
      }
    }
    // left is the index if found, or the insertion point otherwise.
    // ~left is a shorthand for -left - 1.
    return found ? left : ~left;
  };
  
  
  /**
   * Sorts the specified array into ascending order.  If no opt_compareFn is
   * specified, elements are compared using
   * <code>goog.array.defaultCompare</code>, which compares the elements using
   * the built in < and > operators.  This will produce the expected behavior
   * for homogeneous arrays of String(s) and Number(s), unlike the native sort,
   * but will give unpredictable results for heterogenous lists of strings and
   * numbers with different numbers of digits.
   *
   * This sort is not guaranteed to be stable.
   *
   * Runtime: Same as <code>Array.prototype.sort</code>
   *
   * @param {Array<T>} arr The array to be sorted.
   * @param {?function(T,T):number=} opt_compareFn Optional comparison
   *     function by which the
   *     array is to be ordered. Should take 2 arguments to compare, and return a
   *     negative number, zero, or a positive number depending on whether the
   *     first argument is less than, equal to, or greater than the second.
   * @template T
   */
  goog.array.sort = function(arr, opt_compareFn) {
    // TODO(arv): Update type annotation since null is not accepted.
    arr.sort(opt_compareFn || goog.array.defaultCompare);
  };
  
  
  /**
   * Sorts the specified array into ascending order in a stable way.  If no
   * opt_compareFn is specified, elements are compared using
   * <code>goog.array.defaultCompare</code>, which compares the elements using
   * the built in < and > operators.  This will produce the expected behavior
   * for homogeneous arrays of String(s) and Number(s).
   *
   * Runtime: Same as <code>Array.prototype.sort</code>, plus an additional
   * O(n) overhead of copying the array twice.
   *
   * @param {Array<T>} arr The array to be sorted.
   * @param {?function(T, T): number=} opt_compareFn Optional comparison function
   *     by which the array is to be ordered. Should take 2 arguments to compare,
   *     and return a negative number, zero, or a positive number depending on
   *     whether the first argument is less than, equal to, or greater than the
   *     second.
   * @template T
   */
  goog.array.stableSort = function(arr, opt_compareFn) {
    for (var i = 0; i < arr.length; i++) {
      arr[i] = {index: i, value: arr[i]};
    }
    var valueCompareFn = opt_compareFn || goog.array.defaultCompare;
    function stableCompareFn(obj1, obj2) {
      return valueCompareFn(obj1.value, obj2.value) || obj1.index - obj2.index;
    };
    goog.array.sort(arr, stableCompareFn);
    for (var i = 0; i < arr.length; i++) {
      arr[i] = arr[i].value;
    }
  };
  
  
  /**
   * Sort the specified array into ascending order based on item keys
   * returned by the specified key function.
   * If no opt_compareFn is specified, the keys are compared in ascending order
   * using <code>goog.array.defaultCompare</code>.
   *
   * Runtime: O(S(f(n)), where S is runtime of <code>goog.array.sort</code>
   * and f(n) is runtime of the key function.
   *
   * @param {Array<T>} arr The array to be sorted.
   * @param {function(T): K} keyFn Function taking array element and returning
   *     a key used for sorting this element.
   * @param {?function(K, K): number=} opt_compareFn Optional comparison function
   *     by which the keys are to be ordered. Should take 2 arguments to compare,
   *     and return a negative number, zero, or a positive number depending on
   *     whether the first argument is less than, equal to, or greater than the
   *     second.
   * @template T
   * @template K
   */
  goog.array.sortByKey = function(arr, keyFn, opt_compareFn) {
    var keyCompareFn = opt_compareFn || goog.array.defaultCompare;
    goog.array.sort(arr, function(a, b) {
      return keyCompareFn(keyFn(a), keyFn(b));
    });
  };
  
  
  /**
   * Sorts an array of objects by the specified object key and compare
   * function. If no compare function is provided, the key values are
   * compared in ascending order using <code>goog.array.defaultCompare</code>.
   * This won't work for keys that get renamed by the compiler. So use
   * {'foo': 1, 'bar': 2} rather than {foo: 1, bar: 2}.
   * @param {Array<Object>} arr An array of objects to sort.
   * @param {string} key The object key to sort by.
   * @param {Function=} opt_compareFn The function to use to compare key
   *     values.
   */
  goog.array.sortObjectsByKey = function(arr, key, opt_compareFn) {
    goog.array.sortByKey(arr,
        function(obj) { return obj[key]; },
        opt_compareFn);
  };
  
  
  /**
   * Tells if the array is sorted.
   * @param {!Array<T>} arr The array.
   * @param {?function(T,T):number=} opt_compareFn Function to compare the
   *     array elements.
   *     Should take 2 arguments to compare, and return a negative number, zero,
   *     or a positive number depending on whether the first argument is less
   *     than, equal to, or greater than the second.
   * @param {boolean=} opt_strict If true no equal elements are allowed.
   * @return {boolean} Whether the array is sorted.
   * @template T
   */
  goog.array.isSorted = function(arr, opt_compareFn, opt_strict) {
    var compare = opt_compareFn || goog.array.defaultCompare;
    for (var i = 1; i < arr.length; i++) {
      var compareResult = compare(arr[i - 1], arr[i]);
      if (compareResult > 0 || compareResult == 0 && opt_strict) {
        return false;
      }
    }
    return true;
  };
  
  
  /**
   * Compares two arrays for equality. Two arrays are considered equal if they
   * have the same length and their corresponding elements are equal according to
   * the comparison function.
   *
   * @param {goog.array.ArrayLike} arr1 The first array to compare.
   * @param {goog.array.ArrayLike} arr2 The second array to compare.
   * @param {Function=} opt_equalsFn Optional comparison function.
   *     Should take 2 arguments to compare, and return true if the arguments
   *     are equal. Defaults to {@link goog.array.defaultCompareEquality} which
   *     compares the elements using the built-in '===' operator.
   * @return {boolean} Whether the two arrays are equal.
   */
  goog.array.equals = function(arr1, arr2, opt_equalsFn) {
    if (!goog.isArrayLike(arr1) || !goog.isArrayLike(arr2) ||
        arr1.length != arr2.length) {
      return false;
    }
    var l = arr1.length;
    var equalsFn = opt_equalsFn || goog.array.defaultCompareEquality;
    for (var i = 0; i < l; i++) {
      if (!equalsFn(arr1[i], arr2[i])) {
        return false;
      }
    }
    return true;
  };
  
  
  /**
   * 3-way array compare function.
   * @param {!Array<VALUE>|!goog.array.ArrayLike} arr1 The first array to
   *     compare.
   * @param {!Array<VALUE>|!goog.array.ArrayLike} arr2 The second array to
   *     compare.
   * @param {function(VALUE, VALUE): number=} opt_compareFn Optional comparison
   *     function by which the array is to be ordered. Should take 2 arguments to
   *     compare, and return a negative number, zero, or a positive number
   *     depending on whether the first argument is less than, equal to, or
   *     greater than the second.
   * @return {number} Negative number, zero, or a positive number depending on
   *     whether the first argument is less than, equal to, or greater than the
   *     second.
   * @template VALUE
   */
  goog.array.compare3 = function(arr1, arr2, opt_compareFn) {
    var compare = opt_compareFn || goog.array.defaultCompare;
    var l = Math.min(arr1.length, arr2.length);
    for (var i = 0; i < l; i++) {
      var result = compare(arr1[i], arr2[i]);
      if (result != 0) {
        return result;
      }
    }
    return goog.array.defaultCompare(arr1.length, arr2.length);
  };
  
  
  /**
   * Compares its two arguments for order, using the built in < and >
   * operators.
   * @param {VALUE} a The first object to be compared.
   * @param {VALUE} b The second object to be compared.
   * @return {number} A negative number, zero, or a positive number as the first
   *     argument is less than, equal to, or greater than the second,
   *     respectively.
   * @template VALUE
   */
  goog.array.defaultCompare = function(a, b) {
    return a > b ? 1 : a < b ? -1 : 0;
  };
  
  
  /**
   * Compares its two arguments for inverse order, using the built in < and >
   * operators.
   * @param {VALUE} a The first object to be compared.
   * @param {VALUE} b The second object to be compared.
   * @return {number} A negative number, zero, or a positive number as the first
   *     argument is greater than, equal to, or less than the second,
   *     respectively.
   * @template VALUE
   */
  goog.array.inverseDefaultCompare = function(a, b) {
    return -goog.array.defaultCompare(a, b);
  };
  
  
  /**
   * Compares its two arguments for equality, using the built in === operator.
   * @param {*} a The first object to compare.
   * @param {*} b The second object to compare.
   * @return {boolean} True if the two arguments are equal, false otherwise.
   */
  goog.array.defaultCompareEquality = function(a, b) {
    return a === b;
  };
  
  
  /**
   * Inserts a value into a sorted array. The array is not modified if the
   * value is already present.
   * @param {Array<VALUE>|goog.array.ArrayLike} array The array to modify.
   * @param {VALUE} value The object to insert.
   * @param {function(VALUE, VALUE): number=} opt_compareFn Optional comparison
   *     function by which the array is ordered. Should take 2 arguments to
   *     compare, and return a negative number, zero, or a positive number
   *     depending on whether the first argument is less than, equal to, or
   *     greater than the second.
   * @return {boolean} True if an element was inserted.
   * @template VALUE
   */
  goog.array.binaryInsert = function(array, value, opt_compareFn) {
    var index = goog.array.binarySearch(array, value, opt_compareFn);
    if (index < 0) {
      goog.array.insertAt(array, value, -(index + 1));
      return true;
    }
    return false;
  };
  
  
  /**
   * Removes a value from a sorted array.
   * @param {!Array<VALUE>|!goog.array.ArrayLike} array The array to modify.
   * @param {VALUE} value The object to remove.
   * @param {function(VALUE, VALUE): number=} opt_compareFn Optional comparison
   *     function by which the array is ordered. Should take 2 arguments to
   *     compare, and return a negative number, zero, or a positive number
   *     depending on whether the first argument is less than, equal to, or
   *     greater than the second.
   * @return {boolean} True if an element was removed.
   * @template VALUE
   */
  goog.array.binaryRemove = function(array, value, opt_compareFn) {
    var index = goog.array.binarySearch(array, value, opt_compareFn);
    return (index >= 0) ? goog.array.removeAt(array, index) : false;
  };
  
  
  /**
   * Splits an array into disjoint buckets according to a splitting function.
   * @param {Array<T>} array The array.
   * @param {function(this:S, T,number,Array<T>):?} sorter Function to call for
   *     every element.  This takes 3 arguments (the element, the index and the
   *     array) and must return a valid object key (a string, number, etc), or
   *     undefined, if that object should not be placed in a bucket.
   * @param {S=} opt_obj The object to be used as the value of 'this' within
   *     sorter.
   * @return {!Object} An object, with keys being all of the unique return values
   *     of sorter, and values being arrays containing the items for
   *     which the splitter returned that key.
   * @template T,S
   */
  goog.array.bucket = function(array, sorter, opt_obj) {
    var buckets = {};
  
    for (var i = 0; i < array.length; i++) {
      var value = array[i];
      var key = sorter.call(opt_obj, value, i, array);
      if (goog.isDef(key)) {
        // Push the value to the right bucket, creating it if necessary.
        var bucket = buckets[key] || (buckets[key] = []);
        bucket.push(value);
      }
    }
  
    return buckets;
  };
  
  
  /**
   * Creates a new object built from the provided array and the key-generation
   * function.
   * @param {Array<T>|goog.array.ArrayLike} arr Array or array like object over
   *     which to iterate whose elements will be the values in the new object.
   * @param {?function(this:S, T, number, ?) : string} keyFunc The function to
   *     call for every element. This function takes 3 arguments (the element, the
   *     index and the array) and should return a string that will be used as the
   *     key for the element in the new object. If the function returns the same
   *     key for more than one element, the value for that key is
   *     implementation-defined.
   * @param {S=} opt_obj The object to be used as the value of 'this'
   *     within keyFunc.
   * @return {!Object<T>} The new object.
   * @template T,S
   */
  goog.array.toObject = function(arr, keyFunc, opt_obj) {
    var ret = {};
    goog.array.forEach(arr, function(element, index) {
      ret[keyFunc.call(opt_obj, element, index, arr)] = element;
    });
    return ret;
  };
  
  
  /**
   * Creates a range of numbers in an arithmetic progression.
   *
   * Range takes 1, 2, or 3 arguments:
   * <pre>
   * range(5) is the same as range(0, 5, 1) and produces [0, 1, 2, 3, 4]
   * range(2, 5) is the same as range(2, 5, 1) and produces [2, 3, 4]
   * range(-2, -5, -1) produces [-2, -3, -4]
   * range(-2, -5, 1) produces [], since stepping by 1 wouldn't ever reach -5.
   * </pre>
   *
   * @param {number} startOrEnd The starting value of the range if an end argument
   *     is provided. Otherwise, the start value is 0, and this is the end value.
   * @param {number=} opt_end The optional end value of the range.
   * @param {number=} opt_step The step size between range values. Defaults to 1
   *     if opt_step is undefined or 0.
   * @return {!Array<number>} An array of numbers for the requested range. May be
   *     an empty array if adding the step would not converge toward the end
   *     value.
   */
  goog.array.range = function(startOrEnd, opt_end, opt_step) {
    var array = [];
    var start = 0;
    var end = startOrEnd;
    var step = opt_step || 1;
    if (opt_end !== undefined) {
      start = startOrEnd;
      end = opt_end;
    }
  
    if (step * (end - start) < 0) {
      // Sign mismatch: start + step will never reach the end value.
      return [];
    }
  
    if (step > 0) {
      for (var i = start; i < end; i += step) {
        array.push(i);
      }
    } else {
      for (var i = start; i > end; i += step) {
        array.push(i);
      }
    }
    return array;
  };
  
  
  /**
   * Returns an array consisting of the given value repeated N times.
   *
   * @param {VALUE} value The value to repeat.
   * @param {number} n The repeat count.
   * @return {!Array<VALUE>} An array with the repeated value.
   * @template VALUE
   */
  goog.array.repeat = function(value, n) {
    var array = [];
    for (var i = 0; i < n; i++) {
      array[i] = value;
    }
    return array;
  };
  
  
  /**
   * Returns an array consisting of every argument with all arrays
   * expanded in-place recursively.
   *
   * @param {...*} var_args The values to flatten.
   * @return {!Array<?>} An array containing the flattened values.
   */
  goog.array.flatten = function(var_args) {
    var CHUNK_SIZE = 8192;
  
    var result = [];
    for (var i = 0; i < arguments.length; i++) {
      var element = arguments[i];
      if (goog.isArray(element)) {
        for (var c = 0; c < element.length; c += CHUNK_SIZE) {
          var chunk = goog.array.slice(element, c, c + CHUNK_SIZE);
          var recurseResult = goog.array.flatten.apply(null, chunk);
          for (var r = 0; r < recurseResult.length; r++) {
            result.push(recurseResult[r]);
          }
        }
      } else {
        result.push(element);
      }
    }
    return result;
  };
  
  
  /**
   * Rotates an array in-place. After calling this method, the element at
   * index i will be the element previously at index (i - n) %
   * array.length, for all values of i between 0 and array.length - 1,
   * inclusive.
   *
   * For example, suppose list comprises [t, a, n, k, s]. After invoking
   * rotate(array, 1) (or rotate(array, -4)), array will comprise [s, t, a, n, k].
   *
   * @param {!Array<T>} array The array to rotate.
   * @param {number} n The amount to rotate.
   * @return {!Array<T>} The array.
   * @template T
   */
  goog.array.rotate = function(array, n) {
    goog.asserts.assert(array.length != null);
  
    if (array.length) {
      n %= array.length;
      if (n > 0) {
        goog.array.ARRAY_PROTOTYPE_.unshift.apply(array, array.splice(-n, n));
      } else if (n < 0) {
        goog.array.ARRAY_PROTOTYPE_.push.apply(array, array.splice(0, -n));
      }
    }
    return array;
  };
  
  
  /**
   * Moves one item of an array to a new position keeping the order of the rest
   * of the items. Example use case: keeping a list of JavaScript objects
   * synchronized with the corresponding list of DOM elements after one of the
   * elements has been dragged to a new position.
   * @param {!(Array|Arguments|{length:number})} arr The array to modify.
   * @param {number} fromIndex Index of the item to move between 0 and
   *     {@code arr.length - 1}.
   * @param {number} toIndex Target index between 0 and {@code arr.length - 1}.
   */
  goog.array.moveItem = function(arr, fromIndex, toIndex) {
    goog.asserts.assert(fromIndex >= 0 && fromIndex < arr.length);
    goog.asserts.assert(toIndex >= 0 && toIndex < arr.length);
    // Remove 1 item at fromIndex.
    var removedItems = goog.array.ARRAY_PROTOTYPE_.splice.call(arr, fromIndex, 1);
    // Insert the removed item at toIndex.
    goog.array.ARRAY_PROTOTYPE_.splice.call(arr, toIndex, 0, removedItems[0]);
    // We don't use goog.array.insertAt and goog.array.removeAt, because they're
    // significantly slower than splice.
  };
  
  
  /**
   * Creates a new array for which the element at position i is an array of the
   * ith element of the provided arrays.  The returned array will only be as long
   * as the shortest array provided; additional values are ignored.  For example,
   * the result of zipping [1, 2] and [3, 4, 5] is [[1,3], [2, 4]].
   *
   * This is similar to the zip() function in Python.  See {@link
   * http://docs.python.org/library/functions.html#zip}
   *
   * @param {...!goog.array.ArrayLike} var_args Arrays to be combined.
   * @return {!Array<!Array<?>>} A new array of arrays created from
   *     provided arrays.
   */
  goog.array.zip = function(var_args) {
    if (!arguments.length) {
      return [];
    }
    var result = [];
    for (var i = 0; true; i++) {
      var value = [];
      for (var j = 0; j < arguments.length; j++) {
        var arr = arguments[j];
        // If i is larger than the array length, this is the shortest array.
        if (i >= arr.length) {
          return result;
        }
        value.push(arr[i]);
      }
      result.push(value);
    }
  };
  
  
  /**
   * Shuffles the values in the specified array using the Fisher-Yates in-place
   * shuffle (also known as the Knuth Shuffle). By default, calls Math.random()
   * and so resets the state of that random number generator. Similarly, may reset
   * the state of the any other specified random number generator.
   *
   * Runtime: O(n)
   *
   * @param {!Array<?>} arr The array to be shuffled.
   * @param {function():number=} opt_randFn Optional random function to use for
   *     shuffling.
   *     Takes no arguments, and returns a random number on the interval [0, 1).
   *     Defaults to Math.random() using JavaScript's built-in Math library.
   */
  goog.array.shuffle = function(arr, opt_randFn) {
    var randFn = opt_randFn || Math.random;
  
    for (var i = arr.length - 1; i > 0; i--) {
      // Choose a random array index in [0, i] (inclusive with i).
      var j = Math.floor(randFn() * (i + 1));
  
      var tmp = arr[i];
      arr[i] = arr[j];
      arr[j] = tmp;
    }
  };
  
  
  /**
   * Returns a new array of elements from arr, based on the indexes of elements
   * provided by index_arr. For example, the result of index copying
   * ['a', 'b', 'c'] with index_arr [1,0,0,2] is ['b', 'a', 'a', 'c'].
   *
   * @param {!Array<T>} arr The array to get a indexed copy from.
   * @param {!Array<number>} index_arr An array of indexes to get from arr.
   * @return {!Array<T>} A new array of elements from arr in index_arr order.
   * @template T
   */
  goog.array.copyByIndex = function(arr, index_arr) {
    var result = [];
    goog.array.forEach(index_arr, function(index) {
      result.push(arr[index]);
    });
    return result;
  };
  