Lambda the Ultimate

User level transactional programming in Haskell, Peter Thiemann, 2006 Haskell Workshop.

Correct handling of concurrently accessed external resources is a demanding problem in programming. The standard approaches rely on database transactions or concurrency mechanisms like locks. The paper considers two such resources, global variables and databases, and defines transactional APIs for them in Haskell. The APIs provide a novel flavor of user-level transactions which are particularly suitable in the context of web-based systems. This suitability is demonstrated by providing a second implementation in the context of WASH, a Haskell-based Web programming system. The underlying implementation framework works for both kinds of resources and can serve as a blueprint for further implementations of user-level transactions. The Haskell type system provides an encapsulation of the transactional scope that avoids unintended breakage of the transactional guarantees.

I thought this was an interesting paper because it gives a concrete example of a case where you want transactions, but positively don't want the full suite of ACID properties. Maybe it's not so surprising to those hardcore software architects in our audience who go to sleep with Jim Gray and Andreas Reuter's book under their pillows, though. :)

At the recent C4[1] conference, Tim Burks announced a new language he designed, called Nu.

He says the following about it:

Nu is a new programming language that binds the expressive power of Lisp to the pervasiveness and machine-level efficiency of C by building on the power and flexibility of Objective-C.

...

Nu is object-oriented and functional. It is written in Lisp-like S-expressions but conforms to no preexisting Lisp standard.

Tim says that he started out from an effort to bridge Ruby to Objective-C, but the myriad of impedance mismatches led him to develop a new language that he can use instead of Ruby atop of Objective-C:

Instead of grafting two mature and overlapping language implementations together, I wrote Nu on, with, and for Objective-C. Instead of being problems to be bridged, the rich set of Objective-C classes became the building blocks of Nu.

Earlier in the introduction he says:

As a result, Nu has deep access to its own implementation. That gives its users an unusual ability to explore and understand Nu. Where there is understanding, there are few surprises.

Here is a diagram showing all the main programming paradigms and their relationships. This is quite different from the usual diagram which just shows programming languages. This diagram condenses a lot of information in a compact way. If your favorite language is not mentioned here, make a convincing argument and I may add it. If you find any errors, please let me know. I will take all people's comments into account to improve the diagram. Note to Unix aficionados: the diagram was made using xfig running on Mac OS X.

Edit: here is the latest updated diagram.