[chrisjsmith]

SICP covers this too: http://mitpress.mit.edu/sicp/full-text/book/book-Z-H-28.html...

The references are better than the posted link.

I have found a couple of uses for this in the past and deparately tried to port the examples to C# (unsuccessfully).

[shriphani]

I agree. I had to use NDP for solving a few CSPs recently. SICP was a godsend.