Why can I invoke an HSQL function with SELECT but not CALL?

Question

According to the HSQL documentation only SQL procedures require CALL syntax. I am writing a SQL function but I cannot SELECT from it. I can only CALL it. Can anyone see something I've missed? Here is my code

public static void main(String[] args) throws Exception {
    Class<?> driverClass = Class.forName("org.hsqldb.jdbcDriver");
    JDBCDriver driver = (JDBCDriver) driverClass.newInstance();
    Properties props = new Properties();
    props.setProperty("user", "sa");
    props.setProperty("password", "");
    Connection c = driver.connect("jdbc:hsqldb:mem:aname", props);
    execute(c, "CREATE TABLE T (i INT)");
    execute(c, "INSERT INTO T VALUES (1)");
    execute(c, "CREATE FUNCTION f() RETURNS TABLE (i INT) READS SQL DATA " +
            " RETURN TABLE (SELECT * FROM T)");
    System.out.println("Call returns the ResultSet:");
    execute(c, "{ CALL f() }");
    try {
        execute(c, "SELECT * FROM f()");
    } catch (Exception e) {
        System.out.println("Select throws the exception:");
        System.out.println(e);
    }
}

private static void execute(Connection c, String sql) throws SQLException {
    Statement s = c.createStatement();
    try {
        s.execute(sql);
        ResultSet rs = s.getResultSet();
        if (rs != null) {
            printResultSet(rs);
        }
    } finally {
        s.close();
    }
}

private static void printResultSet(ResultSet rs) throws SQLException {
    try {
        while (rs.next()) {
            int columnCount = rs.getMetaData().getColumnCount();
            for (int i = 1; i <= columnCount; i++) {
                System.out.println(rs.getObject(i));
            }
        }
    } finally {
        rs.close();
    }
}

I get the output:

Call returns the ResultSet:
1
Select throws the exception:
java.sql.SQLSyntaxErrorException: user lacks privilege or object not found: F

Answer 1

The correct syntax for selecting the table returned by this function is as follows:

SELECT * FROM TABLE(F())