'use strict';
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// https://github.com/tc39/proposal-iterator-helpers
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var $ = require('../internals/export');
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var global = require('../internals/global');
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var call = require('../internals/function-call');
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var aCallable = require('../internals/a-callable');
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var anObject = require('../internals/an-object');
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var getIteratorMethod = require('../internals/get-iterator-method');
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var createIteratorProxy = require('../internals/iterator-create-proxy');
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var iteratorClose = require('../internals/iterator-close');
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var TypeError = global.TypeError;
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var IteratorProxy = createIteratorProxy(function () {
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var iterator = this.iterator;
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var mapper = this.mapper;
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var result, mapped, iteratorMethod, innerIterator;
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while (true) {
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try {
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if (innerIterator = this.innerIterator) {
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result = anObject(call(this.innerNext, innerIterator));
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if (!result.done) return result.value;
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this.innerIterator = this.innerNext = null;
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}
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result = anObject(call(this.next, iterator));
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if (this.done = !!result.done) return;
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mapped = mapper(result.value);
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iteratorMethod = getIteratorMethod(mapped);
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if (!iteratorMethod) {
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throw TypeError('.flatMap callback should return an iterable object');
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}
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this.innerIterator = innerIterator = anObject(call(iteratorMethod, mapped));
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this.innerNext = aCallable(innerIterator.next);
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} catch (error) {
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iteratorClose(iterator, 'throw', error);
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}
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}
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});
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$({ target: 'Iterator', proto: true, real: true, forced: true }, {
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flatMap: function flatMap(mapper) {
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return new IteratorProxy({
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iterator: anObject(this),
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mapper: aCallable(mapper),
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innerIterator: null,
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innerNext: null
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});
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}
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});
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