//Dictionary//////////////////////////////////

function Dictionary() {

    this.length = 0;

}

Dictionary.prototype.lookup = function(key) {

    return (this[key]);

}

Dictionary.prototype.add = function(key, item) {

    if (!this.exists(key)) this.length++;

    this[key] = item;

}

Dictionary.prototype.remove = function(key) {

    this[key] = null;

    if (this.length > 0) this.length--;

}

Dictionary.prototype.exists = function(key) {

    return this[key] != null;

}

/////////////////////////////////////////////////