generic-set.js

module.exports = GenericSet;
function GenericSet() {
    throw new Error("Can't construct. GenericSet is a mixin.");
}

GenericSet.prototype.union = function (that) {
    var union =  this.constructClone(this);
    union.addEach(that);
    return union;
};

GenericSet.prototype.intersection = function (that) {
    return this.constructClone(this.filter(function (value) {
        return that.has(value);
    }));
};

GenericSet.prototype.difference = function (that) {
    var union =  this.constructClone(this);
    union.deleteEach(that);
    return union;
};

GenericSet.prototype.symmetricDifference = function (that) {
    var union = this.union(that);
    var intersection = this.intersection(that);
    return union.difference(intersection);
};

GenericSet.prototype.equals = function (that, equals) {
    var self = this;
    return (
        Object.can(that, "reduce") &&
        this.length === that.length &&
        that.reduce(function (equal, value) {
            return equal && self.has(value, equals);
        }, true)
    );
};

// W3C DOMTokenList API overlap (does not handle variadic arguments)

GenericSet.prototype.contains = function (value) {
    return this.has(value);
};

GenericSet.prototype.remove = function (value) {
    return this["delete"](value);
};

GenericSet.prototype.toggle = function (value) {
    if (this.has(value)) {
        this["delete"](value);
    } else {
        this.add(value);
    }
};