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The Art of the Propagator

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".

By neelk at 2009-03-24 23:47 | DSL | Implementation | Paradigms | other blogs | 23502 reads

Re: HTML guidelines

Is it generally ok to post content with character entity references (like ⇒ for ⇒)? I mean how many people won't be able to read that?

I'd say if you need it, use it, and hopefully anyone who can't see it will say so.

Also, I remember seeing discussion on using "style" tag, but without any conclusion. Could we standardize some style classes by inclusion of their definitions in LtU CSS file(s)?

The LtU CSS files will do this very soon.

I think we need classes for at least quoting previous comments (italic?) and for excerpts (blue italic?

Yes. The <blockquote> element should be used for block quotes, naturally. For inline quotes, I think we'll use the Q element, although I see it's been deprecated/removed in XHTML 2 (but its replacement isn't yet supported by browsers).

should we break tradition to make it different in color from default links?).

I was thinking of using the fairly standard approach of inserting a vertical bar in the margin of a blockquote, which ought to make such quotes unambiguous, regardless of their color. For inline quotes marked up with Q, I think we'll avoid blue.

By Anton van Straaten at Mon, 2004-08-02 16:37 | parent | login or register to post comments