iterable-iterator/range

import assert from 'assert';

import Range from './Range.js';
import backwardRangeIterator from './backwardRangeIterator.js';

export default class BackwardRange extends Range {
    /**
     * Constructor.
     *
     * @param {number} start
     * @param {number} stop
     * @param {number} step
     */
    constructor(start, stop, step) {
        assert(step !== 0);
        assert(step < 0);
        super(
            start,
            stop,
            step,
            start <= stop ? 0 : 1 + Math.floor((stop - start + 1) / step),
        );
    }

    /**
     * @returns {IterableIterator<number>}
     */
    [Symbol.iterator]() {
        return backwardRangeIterator(this.start, this.stop, this.step);
    }

    /**
     * Has.
     *
     * @param {number} x
     * @returns {boolean}
     */
    has(x) {
        if (!Number.isInteger(x)) return false;
        if (x <= this.stop) return false;
        if (x > this.start) return false;
        return (this.start - x) % this.step === 0;
    }
}