/*
 *  call-seq:
 *     sort_field.type -> symbol
 *  
 *  Return the type of sort. Should be one of; +:auto+, +:integer+, +:float+,
 *  +:string+, +:byte+, +:doc_id+ or +:score+.
 */
static VALUE
frt_sf_get_type(VALUE self)
{
    GET_SF();
    switch (sf->type) {
        case SORT_TYPE_BYTE:    return sym_byte;
        case SORT_TYPE_INTEGER: return sym_integer;
        case SORT_TYPE_FLOAT:   return sym_float;
        case SORT_TYPE_STRING:  return sym_string;
        case SORT_TYPE_AUTO:    return sym_auto;
        case SORT_TYPE_DOC:     return sym_doc_id;
        case SORT_TYPE_SCORE:   return sym_score;
    }
    return Qnil;
}