Lambda the Ultimate

I know the type system discussion is taking its toll, but I am sure things would be more interesting around here if we had more news items.

So all you editors out there: How about sharing?

Slideshow: Functional Presentations. Findler, Flatt. ICFP 2004.

Nothing earth shattering, but a nice example of DSL design none the less.

Might be useful for teaching (as well as for creating slideshows...)

You may have noticed that the type systems thread dominates the Recent Posts list. :/ Wouldn't it be nice if Recent Posts only showed the last n posts in a topic, and concluded with a link like "... (click for more) ..." or something if necessary? Or even, if you were logged in, if it showed only the new (asterisked) posts in each thread?

Daan Leijen. Submitted to the 32nd ACM Symposium on Principles of Programming Languages (POPL'05), Long beach California, January 12, 2005. (PDF, BibTeX)

This paper describes a type system for extensible records and variants with first-class labels; labels are polymorphic and can be passed as arguments. This increases the expressiveness of conventional record calculi significantly, and we show how we can encode intersection types, closed-world overloading, type case, label selective calculi, and first-class messages. We formally motivate the need for row equality predicates to express type constraints in the presence of polymorphic labels. This naturally leads to an orthogonal treatment of unrestricted row polymorphism that can be used to express first-class patterns. Based on the theory of qualified types, we present an effective type inference algorithm and efficient compilation method. The type inference algorithm, including the discussed extensions, is fully implemented in the experimental Morrow compiler.

Always trust Daan to come up with something both elegant and practical...! However the examples involving bottom (undefined) labels left me skeptical.

I started to use the "Flat list - expanded" mode because the indentation was (in some discussions) getting too large, but in this mode we don't know the parent of a post (which make things a little confusing). IMO it would be nice to have parent links, regardless of view mode.

Slate 0.3 has been released. Slate is a language similar to Smalltalk with a prototype based object system and multi-method dispatch.