A bug of the function "DataFolderExists"?

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Tue, 05/17/2011 - 09:35 am

I am not sure whether it is a bug of the function "DataFolderExists" but would like to invite you guys who are interesting in it to test.

I just found the function "DataFolderExists" failed to return the result correctly if the hierarchy of the data folders contained at least one folder began with numbers. For example, if the hierarchy looks like root:t:tt:2tt, DataFolderExists("root:t:tt:2tt") will return 0, but if the hierarchy is like root:t:tt:tt2, DataFolderExists("root:t:tt:tt2") will return 1. The same thing happens in the case of root:t:2t:tt2. The most funny thing is that, if you set the default folder to root:t first, and DataFolderExists("2t") will correctly return 1.

Any comment or suggestion?
Because it starts with a number instead of a letter, "2tt" is a "liberal" name.

Liberal names generally need to be quoted with a single quote. This will work:
Print DataFolderExists("root:t:tt:'2tt'")  // Liberal name is quoted with single quotes


There is one very tricky exception. If you have a simple name rather than a path in a string, it must NOT be quoted:
Print DataFolderExists("'2tt'")  // WRONG
Print DataFolderExists("2tt")  // RIGHT


You can read about this by executing:
DisplayHelpTopic "Programming with Liberal Names"


It's pretty difficult to program in a liberal-name-safe way. If you use a liberal name only occasionally, you may write code that is not liberal-name-safe but you might not know it. There are two solutions:

1. Test all of your routines with liberal names.
2. Don't use liberal names.

If you use liberal names, you will need to refresh your memory about the rules by reading the help section referenced above from time-to-time.

May 17, 2011 at 10:40 am - Permalink

The cause of the problem is that the subfolder name "2tt" does not follow the standard naming rule that objects must start with an alpha character. The liberal name "2tt" can be used if it is enclosed in single quotes as in:

DataFolderExists(("root:t:tt:'2tt'")

You can learn more about liberal object names and data folder syntax by typing the following in the command window:

DisplayHelpTopic "Object Names[Liberal Object Names]"

DisplayHelpTopic "Data Folders[Data Folder Syntax]"

They will pull up topics from the help files.

May 17, 2011 at 10:46 am - Permalink

Thanks a lot.

I admit that I totally forget the limitation of the liberal name.

May 17, 2011 at 01:48 pm - Permalink