Maybe it was initially supposed to be a sort of "3-value boolean" (true/false/undefined) and not a standard bool. You can (rarely) meet this pattern in c++ if y

Maybe it was initially supposed to be a sort of "3-value boolean" (true/false/undefined) and not a standard bool. You can (rarely) meet this pattern in c++ if you use boost::tribool or in c# if you have a nullable bool. There is probably similar thing in other languages.