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Postings from June 2001
When you blass an object in Perl, you give it exactly one type. The @ISA variable allows that type to refer to many other classes as the inheritance tree. @ISA is a list, but ref($obj) isn't. This means that you sometimes have to create a lot of useless classes to work around this limitation. A simple example: Imagine you have a class "Person". A Person can be Male or Female. Thats one set of subclasses. But a Person can also be Employed or Unemployed. So I might want to say bless $self, qw(Employed Male); In Perl5 I am forced to create 4 new classes: Employed_Male, Employed_Female, Unemployed_Male, Unemployed_Female. The combinatorial explosion can, well, explode! The other standard solution is to add a "Person has-a Employment_Status" relationship, but that doesn't feel much better. Its just another way of programming round a weakness in the object models of most mainstream languages Can anyone see any problems with making C<bless> and C<ref> work with lists? C<isa> is not effected. We might want some magic to ensure 'ref($foo) eq "bar"' still works as expected. Dave. -- Dave Whipp, Senior Verification Engineer, Fast-Chip inc., 950 Kifer Rd, Sunnyvale, CA. 94086 tel: 408 523 8071; http://www.fast-chip.com Opinions my own; statements of fact may be in error.