> Or, you can create a second null-like type in the language, name it 'undefined' perhaps, and return that when the key doesn't exist.
No, this isn't a solution. This is like terminating C strings with 0 characters, or terminating TSV fields with tabs. It sounds like it makes sense, until you ask "what if the terminator occurs within the data?"
Eventually someone's going to need to store undefined. It's no different than null. If it were a competence issue (which it isn't), we'd be saying that storing null in the hash table was a mistake, not something to work around with null2.
No, this isn't a solution. This is like terminating C strings with 0 characters, or terminating TSV fields with tabs. It sounds like it makes sense, until you ask "what if the terminator occurs within the data?"
Eventually someone's going to need to store undefined. It's no different than null. If it were a competence issue (which it isn't), we'd be saying that storing null in the hash table was a mistake, not something to work around with null2.