src/0-core/split/deepR.js

import {Deep} from '../../3-tree/index.js';
import {delay} from '../../4-lazy/index.js';
import {_from_digit, _digit} from '../_fast/index.js';

/**
 * @param {Measure} M
 * @param {Digit} left
 * @param {FingerTree} middle
 * @param {Array} right
 */
export function deepR(M, left, middle, right) {
	if (right.length === 0) {
		if (middle.isEmpty()) return _from_digit(M, left);

		return new Deep(
			M,
			left,
			delay(() => middle.init()),
			middle.last().digit(),
		);
	}

	return new Deep(M, left, middle, _digit(right));
}