From: djberg96@... (Daniel Berger)
Date: 2004-04-03T03:04:24+09:00
Subject: parent of TrueClass, FalseClass, continued

Simon Strandgaard wrote:

>Then it would be easy to add a Maybe class ;-)

You're joking a little, I know, but consider the case of Oracle. 
Well, ok, Oracle PL/SQL.  In Ruby, nil is false.  However, in Oracle
PL/SQL you have a Boolean data type that is either true, false or null
(i.e. unknown).

Having a Boolean parent class could make object-relational mapping
layer packages, like Kansas, a bit easier (though I admit, I'm
guessing here).  It could also be useful in DBI itself, where I could
retrieve data from a column with a NULL value as nil, but which
wouldn't equate to false.  From there I can perform tri-state code
logic, ala PL/SQL.

For example, consider a table with a VARCHAR2(1) column called
"is_deceased" for a list of movie actors and actresses.  I could
either have 'Y' or 'N' to indicate true or false.  But if there's no
constraint on that column *it could also be NULL*, which is NOT the
same as false.  See what I mean?

It could also be handy for that magical day when someone finally gets
around to embedding Ruby within Oracle, ala the PL/SQL Ruby module
that already exists for Postgres, or extproc_perl for Oracle.

As someone else already mentioned, it can also make unit testing
either.  Instead of "is this value true or is this value false", I can
perform this operation as one "is this value a boolean".  That, again,
may be useful in the database side of things.

Well, that's all I can think of for now.  Maybe some other folks could
provide additional examples where it would be useful.

Just my .02

Regards,

Dan

PS - Damn - google groups doesn't seem to be picking up the ML traffic
again, so I've had to create a new thread since I don't subscribe to
the ML.  My apologies.