data-structure-algebra/doubly-linked-list

import assert from 'assert';

import Node from './Node.js';

/**
 * Compute the length of a non-empty list.
 *
 * @param {Node} x First node of the input list.
 * @return {number} The length of the input list.
 */

export default function _len(x) {
    assert(x instanceof Node);
    let n = 1;
    let y = x.next;
    while (y !== null) {
        ++n;
        y = y.next;
    }

    return n;
}