Re: EDS:: NO_TABLE, db_table_list()
- Posted by K_D_R Feb 11, 2012
- 1383 views
BINGO! When I run the first block of code without evaluating dbtblst for atom status on a new db which has no table, I get a "true false condition must be an atom" for the line:
if dbtblst = NO_TABLE then
Shouldn't NO_Table be an atom?
NO_TABLE is an atom. However, according to the documentation, db_table_list() returns a sequence that contains a list of table names. If this sequence is empty, there are no tables in the database.
The documentation currently makes no reference to an empty sequence. I believe the documentation should be improved by appending your last sentence above to the description of what db_table_list() returns:
Returns: A sequence, of all the table names in the current database. Each element of this sequence is a sequence, the name of a table. If this sequence is empty, there are no tables in the database.
The NO_TABLE error code is returned only by those functions that can take a table name as a parameter and the supplied table name is not known in the current database. ... The db_table_list() function does not accept a table name as a parameter so it does not return NO_TABLE.
I somehow miss the above information in the documentation. Given the current state of the documentation search facilities, it could be there and easily missed. What I do see is this:
8.28.3.4 NO_TABLE include std/eds.e namespace eds public enum NO_TABLE no table was found.
No table was found. Certainly, no table was found by db_table_list() when the current db had no tables. Shouldn't that statement be replaced by a more accurate description, such as Derek has provided above?:
8.28.3.4 NO_TABLE include std/eds.e namespace eds public enum NO_TABLE The ##NO_TABLE## error code is returned only by those functions that can take a table name as a parameter and the supplied table name is not known in the current database.
Also, as a database can legally contain no tables, it is never an error condition for db_table_list() to return an empty list. The NO_TABLE is an error condition so its not appropriate for db_table_list() to return that code.
Following that logic: as a database can legally not have a specific table sought by a certain function, it would not be an error to return an empty sequence, but an error code is returned instead.
A database can legally contain no tables and it can legally contain no tables with a name specified in the parameters of a function.
Isn't it is just as much of an error not to find any table at all in response to a query for a list of tables as it is not to find a specific table in response to a query for a table with a particular name? If there is a benefit in returning the NO_TABLE error code in the latter case, shouldn't that benefit be extended to the former case?
Jiri Babor did not suffer fools gladly. He commented a block of code in one of his programs:
-- in case of idiots
I smiled, knowing Jiri was looking out for me.
Regards, Kenneth Rhodes
