They are described (using Scheme) in Alexey Radul and Gerald Sussman's ["The Art of the Propagator"](http://web.mit.edu/~axch/www/art.pdf) as well as in Alexey Radul's thesis on [Propagation Networks](http://groups.csail.mit.edu/genesis/papers/radul%202009.pdf).
This package explores design options for propagators in Haskell. The primary innovation here (beyond the published work) is the use of observable sharing to let us take a more direct form of programming and transform it back and forth to the propagator style.
Contact Information
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Contributions and bug reports are welcome!
Please feel free to contact me through github or on the #haskell IRC channel on irc.freenode.net.