functional-data-structure/finger-tree

import {Tree} from '../3-tree/base/Tree.js';

export function Lazy(thunk) {
    this.tree = null;
    this.thunk = thunk;
}

Lazy.prototype = new Tree();

Lazy.prototype.force = function () {
    if (this.tree === null) {
        this.tree = this.thunk();
        this.thunk = null;
    }

    return this.tree;
};

Lazy.prototype.isEmpty = function () {
    return this.force().isEmpty();
};

Lazy.prototype.measure = function () {
    return this.force().measure();
};

Lazy.prototype.head = function () {
    return this.force().head();
};

Lazy.prototype.last = function () {
    return this.force().last();
};

Lazy.prototype.cons = function (value) {
    return this.force().cons(value);
};

Lazy.prototype.push = function (value) {
    return this.force().push(value);
};

Lazy.prototype.tail = function () {
    return this.force().tail();
};

Lazy.prototype.init = function () {
    return this.force().init();
};

Lazy.prototype.splitTree = function (p, i) {
    return this.force().splitTree(p, i);
};

Lazy.prototype.split = function (p) {
    return this.force().split(p);
};

Lazy.prototype.concat = function (other) {
    return this.force().concat(other);
};

Lazy.prototype[Symbol.iterator] = function () {
    return this.force()[Symbol.iterator]();
};

Lazy.prototype.reversed = function () {
    return this.force().reversed();
};