Steve Yegge's comment in "Ten Challenges": It (Types and Programming Languages, Benjamin C. Pierce) spends a lot of time covering the ML type system, which is one of the strongest, most "elegant" type systems out there, and you'll find more and more books talking about it. And more and more languages are starting to use it. It's considered one of the best type systems in the world, because it gives you a lot of flexibility and Perl-like expressiveness, while maintaining strong compile-time guarantees that you're not assigning the wrong type of data to a value. It's basically the best of the strong-typing and dynamic-typing worlds, because you don't have to declare most of your type tags.
http://blog.steveklabnik.com/posts/2010-07-17-what-to-know-before-debating-type-systems
Steve Yegge's comment in "Ten Challenges": It (Types and Programming Languages, Benjamin C. Pierce) spends a lot of time covering the ML type system, which is one of the strongest, most "elegant" type systems out there, and you'll find more and more books talking about it. And more and more languages are starting to use it. It's considered one of the best type systems in the world, because it gives you a lot of flexibility and Perl-like expressiveness, while maintaining strong compile-time guarantees that you're not assigning the wrong type of data to a value. It's basically the best of the strong-typing and dynamic-typing worlds, because you don't have to declare most of your type tags.