private Number getOr(Number defaultValue, int valueIndex, String[] values) {
        if (valueIndex >= values.length) return defaultValue;
        if (values[valueIndex] == null) return defaultValue;
        if (values[valueIndex].isEmpty()) return defaultValue;
        return asNumber(values[valueIndex]);
    }
Sets the number expression of this - a number or range following the syntax specified in the class javadoc
container-search/src/main/java/com/yahoo/prelude/query/IntItem.java