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    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
  // ------------------

  // Create a function bound to a given object (assigning `this`, and arguments,
  // optionally). Delegates to **ECMAScript 5**'s native `Function.bind` if
  // available.
  _.bind = function(func, context) {
    if (func.bind === nativeBind && nativeBind) return nativeBind.apply(func, slice.call(arguments, 1));
    var args = slice.call(arguments, 2);
    return function() {
      return func.apply(context, args.concat(slice.call(arguments)));
    };
  };

  // Partially apply a function by creating a version that has had some of its
  // arguments pre-filled, without changing its dynamic `this` context.
  _.partial = function(func) {
    var args = slice.call(arguments, 1);
    return function() {
      return func.apply(this, args.concat(slice.call(arguments)));
    };
  };

  // 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, result;
    var previous = 0;
    var later = function() {
      previous = new Date;
      timeout = null;
      result = func.apply(context, args);
    };
    return function() {
      var now = new Date;
      var remaining = wait - (now - previous);
      context = this;
      args = arguments;
      if (remaining <= 0) {
        clearTimeout(timeout);
        timeout = null;
        previous = now;
        result = func.apply(context, args);
      } else if (!timeout) {
        timeout = setTimeout(later, remaining);
      }
      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, result;
    return function() {
      var context = this, args = arguments;
      var later = function() {
        timeout = null;
        if (!immediate) result = func.apply(context, args);
      };
      var callNow = immediate && !timeout;
      clearTimeout(timeout);
      timeout = setTimeout(later, wait);
      if (callNow) result = func.apply(context, args);
      return result;
    };
  };

  // 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;
      memo = func.apply(this, arguments);
      func = null;
      return memo;
    };
  };

  // 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];
      push.apply(args, arguments);
      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 = [];