(function (tree) {

tree.Keyword = function (value) { this.value = value };
tree.Keyword.prototype = {
    type: "Keyword",
    eval: function () { return this; },
    toCSS: function () { return this.value; },
    compare: function (other) {
        if (other instanceof tree.Keyword) {
            return other.value === this.value ? 0 : 1;
        } else {
            return -1;
        }
    }
};

tree.True = new(tree.Keyword)('true');
tree.False = new(tree.Keyword)('false');

})(require('../tree'));