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var arrayReduce = require('./_arrayReduce'),
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    baseEach = require('./_baseEach'),
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    baseIteratee = require('./_baseIteratee'),
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    baseReduce = require('./_baseReduce'),
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    isArray = require('./isArray');
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/**
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 * Reduces `collection` to a value which is the accumulated result of running
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 * each element in `collection` thru `iteratee`, where each successive
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 * invocation is supplied the return value of the previous. If `accumulator`
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 * is not given, the first element of `collection` is used as the initial
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 * value. The iteratee is invoked with four arguments:
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 * (accumulator, value, index|key, collection).
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 *
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 * Many lodash methods are guarded to work as iteratees for methods like
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 * `_.reduce`, `_.reduceRight`, and `_.transform`.
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 *
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 * The guarded methods are:
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 * `assign`, `defaults`, `defaultsDeep`, `includes`, `merge`, `orderBy`,
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 * and `sortBy`
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 *
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 * @static
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 * @memberOf _
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 * @since 0.1.0
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 * @category Collection
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 * @param {Array|Object} collection The collection to iterate over.
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 * @param {Function} [iteratee=_.identity] The function invoked per iteration.
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 * @param {*} [accumulator] The initial value.
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 * @returns {*} Returns the accumulated value.
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 * @see _.reduceRight
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 * @example
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 *
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 * _.reduce([1, 2], function(sum, n) {
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 *   return sum + n;
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 * }, 0);
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 * // => 3
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 *
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 * _.reduce({ 'a': 1, 'b': 2, 'c': 1 }, function(result, value, key) {
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 *   (result[value] || (result[value] = [])).push(key);
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 *   return result;
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 * }, {});
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 * // => { '1': ['a', 'c'], '2': ['b'] } (iteration order is not guaranteed)
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 */
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function reduce(collection, iteratee, accumulator) {
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  var func = isArray(collection) ? arrayReduce : baseReduce,
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      initAccum = arguments.length < 3;
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  return func(collection, baseIteratee(iteratee, 4), accumulator, initAccum, baseEach);
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}
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module.exports = reduce;
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