module.exports = function (xs, fn) {
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								    var res = [];
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								    for (var i = 0; i < xs.length; i++) {
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								        var x = fn(xs[i], i);
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								        if (isArray(x)) res.push.apply(res, x);
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								        else res.push(x);
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								    }
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								    return res;
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								};
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						|
								
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								var isArray = Array.isArray || function (xs) {
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								    return Object.prototype.toString.call(xs) === '[object Array]';
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								};
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