Method belongsTo

core/src/main/java/org/apache/calcite/sql/SqlKind.java:1780–1782

Returns whether this SqlKind belongs to a given category. A category is a collection of kinds, not necessarily disjoint. For example, QUERY is { SELECT, UNION, INTERSECT, EXCEPT, VALUES, ORDER_BY, EXPLICIT_TABLE }. @param category Category @return Whether this kind belongs to the given

(Collection<SqlKind> category)

   * @return Whether this kind belongs to the given category
   */
  public final boolean belongsTo(Collection<SqlKind> category) {
    return category.contains(this);
  }

  /**
   * If this kind represents a non-standard function, return OTHER_FUNCTION, otherwise