Lambda the Ultimate

Having saiod that, I must also say that I agree with Conor McBride who wrote that anyone who would argue (and I'm not saying you do) that work to try to make more advanced type systems and stronger static guarantees more convenient and well-supported is not necessary because it happens to be possible to bang out this or that example in Haskell as it stands if you think about it hard enough, is adopting the position of the ostrich.

Making type systems more expressive is a worthy goal. You want them to remain decidable (i.e., static), of course. Can we at least agree on that? ;-)

Well worth checking if you are into this sort of thing.

Acute: high-level programming language design for distributed computation

This work is exploring the design space of high-level languages for distributed computation, focussing on typing, naming, and version change. We have designed, formally specified and implemented an experimental language, Acute. This extends an OCaml core to support distributed development, deployment, and execution, allowing type-safe interaction between separately-built programs. It is expressive enough to enable a wide variety of distributed infrastructure layers to be written as simple library code above the byte-string network and persistent store primitives, disentangling the language runtime from communication.

This requires a synthesis of novel and existing features:

• type-safe interaction between programs, with marshal and unmarshal primitives;
• dynamic loading and controlled rebinding to local resources;
• modules and abstract types with abstraction boundaries that are respected by interaction;
• global names, generated either freshly or based on module hashes: at the type level, as runtime names for abstract types; and at the term level, as channel names and other interaction handles;
• versions and version constraints, integrated with type identity;
• local concurrency and thread thunkification; and
• second-order polymorphism with a namecase construct.

The language design deals with the interplay among these features and the core. The semantic definition tracks abstraction boundaries, global names, and hashes throughout compilation and execution, but still admits an efficient implementation strategy.

SIMH, the Computer History Simulation system, is a behavioral simulator for obsolete systems of historic interest. Originally intended as an educational project, it is increasingly being used in long-lived production environments as a substitute for real systems. SIMH is continuously being extended to simulate new machines.

This item isn't directly PL related, but since many LtU regulars are fond of programming language history, I assume there is interest in other apsects of computing history. On top of that, if and when you try to rescue an obsolete language implementation, there's a good chance you are going to need something like SIMH.

This ACM Queue article describes the design issues invloved in building SIMH, and the problems the arise when simulating old hardware systems.