Lambda the Ultimate

For a while I am puzzled by the unsuitability of public and protected - e.g. default access modifiers in many object oriented languages - for design and especially maintenance of APIs. They are so natural in OOP, yet so harmful for anything that needs to be compatible for more than one version that I have to ask: why there are no better alternatives?

I've summarized my thoughts in Clarity of Access Modifiers essay and I'd like to bring it to attention of LtU readers as I am sure some of you will know the reason why we have these fuzzy modifiers. Also some of you may know about languages that offer better alternatives with more clarity. I am looking forward to hear your opinion. Feel free to comment here or at the page's discussion tab.

The list of accepted papers is out for the IFIP Working Conference on Domain Specific Languages. Happily for me, the program reveals much interest in languages for reasoning, decision making, and search. Even among people who are not my coauthors. :)

Declarative programming tends to attract skepticism because it has the reputation of poor and hard-to-control performance. The approach of DSL embedding appears to ameliorate this problem, and the success of SAT solvers appears to chip away at this reputation.

Meanwhile, the call for papers is out for Principles and Practice of Declarative Programming 2009, which has a venerable program committee. The submission deadline is May 7.

The Art of the Propagator, Alexey Radul and Gerald Jay Sussman.

We develop a programming model built on the idea that the basic computational elements are autonomous machines interconnected by shared cells through which they communicate. Each machine continuously examines the cells it is interested in, and adds information to some based on deductions it can make from information from the others. This model makes it easy to smoothly combine expression-oriented and constraint-based programming; it also easily accommodates implicit incremental distributed search in ordinary programs. This work builds on the original research of Guy Lewis Steele Jr. and was developed more recently with the help of Chris Hanson.

I just ran across this tech report. I haven't read it yet, but the subject is particularly well-timed for me, since I just finished a correctness proof for a simple FRP system implemented via imperative dataflow graphs, and so constraint propagation has been much on my mind recently. It's pretty clear that constraint propagation can do things that FRP doesn't, but it's not so clear to me whether this is a case of "more expressiveness" or "more fragile abstractions".