xquery query slicing

       query: function(query, options) {
            options = options || {};
            // FIXME use facets
            var defaultRangeLength = config.defaultRangeLength || 25; // TODO get from settings
            var slice = function() {
                var length,
                    xquery = "";
                if (defaultRangeLength && !(options.start == 0 && options.end == Infinity)) {
                    options.start = options.start || 0;
                    options.end = options.end || Infinity;
                    if ((options.end - options.start) > defaultRangeLength) {
                        options.end = options.start + defaultRangeLength - 1
                    }
                }
                if (options.start >= 0 && options.end) length = options.end - options.start + 1;
                if (options.start >= 0) {
                    xquery = "[" + (options.start + 1) + " to ";
                    xquery += (options.end !== Infinity && (options.end + 1) || "last()") + "]";
                }
                // TODO handle empty start
                return {
                    xquery: xquery,
                    length: length
                }
            }();
        // ...
        }