On Thursday 19 January 2006 06:48, Rob Kinyon wrote: > "Any practical programming language with structural subtyping will > probably let you create and use aliases for type names (so you don't > have to write the full form everywhere). However, the underlying type > system will only consider the structure of the type when doing its > job." > > What's wrong with Perl doing things that way? duck-typing with names > ... sounds like a plan to me ...
Accidental structural equivalence is a problem -- it's one of the things wrong with C's so-called type system, for example. I like to think of roles as nominally-tagged (and checked) structural subtyping. When you're *defining* a type, its structure matters. When you're *using* it, its behavior matters. It would be nice to keep those two separate. -- c
