iteragain/dist/es5/internal/CombinationsIterator.js

Javascript Iterable/Iterator/Generator-function utilities.

import toArray from '../toArray';
/** Creates `size` length subsequences from the input `iterator`. */
var CombinationsIterator = /** @class */ (function () {
    function CombinationsIterator(iterator, size, withReplacement) {
        this.size = size;
        this.withReplacement = withReplacement;
        this.i = 0;
        this.pool = toArray(iterator);
        this.n = this.pool.length;
        if (this.n < this.size)
            this.next = function () { return ({ done: true, value: undefined }); };
        this.indices = this.withReplacement ? new Array(this.size).fill(0) : Array.from({ length: this.size }, function (_, i) { return i; });
        this.indices[this.indices.length - 1]--; // So that the first combination will start at the correct spot.
    }
    Object.defineProperty(CombinationsIterator.prototype, "value", {
        get: function () {
            var _this = this;
            return this.indices.map(function (i) { return _this.pool[i]; });
        },
        enumerable: false,
        configurable: true
    });
    CombinationsIterator.prototype[Symbol.iterator] = function () {
        return this;
    };
    CombinationsIterator.prototype.next = function () {
        if (this.withReplacement) {
            for (this.i = this.size - 1; this.i > -1; this.i--)
                if (this.indices[this.i] !== this.n - 1)
                    break;
            // If the previous for loop finished without breaking, then we've exhausted all combinations:
            if (this.i === -1)
                return { done: true, value: undefined };
            var v = this.indices[this.i] + 1;
            for (var j = this.i; j < this.size; j++)
                this.indices[j] = v;
            return { done: false, value: this.value };
        }
        for (this.i = this.size - 1; this.i > -1; this.i--)
            if (this.indices[this.i] !== this.i + this.n - this.size)
                break;
        // If the previous for loop finished without breaking, then we've exhausted all combinations:
        if (this.i === -1)
            return { done: true, value: undefined };
        this.indices[this.i]++;
        for (var j = this.i + 1; j < this.size; j++)
            this.indices[j] = this.indices[j - 1] + 1;
        return { done: false, value: this.value };
    };
    return CombinationsIterator;
}());
export { CombinationsIterator };
export default CombinationsIterator;
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