31 lines
681 B
Plaintext
31 lines
681 B
Plaintext
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/**
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* Copyright (c) 2013-present, Facebook, Inc.
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*
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* This source code is licensed under the MIT license found in the
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* LICENSE file in the root directory of this source tree.
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*
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* @providesModule countDistinct
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* @flow
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*/
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'use strict';
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var Set = require("./Set");
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var emptyFunction = require("./emptyFunction");
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/**
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* Returns the count of distinct elements selected from an array.
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*/
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function countDistinct<T1, T2>(iter: Iterable<T1>, selector: (item: T1) => T2): number {
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selector = selector || emptyFunction.thatReturnsArgument;
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var set = new Set();
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for (var val of iter) {
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set.add(selector(val));
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}
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return set.size;
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}
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module.exports = countDistinct;
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