neat paper

http://www.cis.upenn.edu/~bcpierce/papers/lenses.pdf

Think of it as "XSLT but not lame" with the added super-useful
property that any transformation you write is guaranteed (by
construction) to be reversible.

I'm still trying to figure out how this relates to darcs.  And to
metafront and <bigwig>.

  - a

-- 
"It's lucky," he added, after a pause, "that there are such a lot of
islands in the world.  I almost envy you, Mr. Watson."

                                                   -- Mustapha Mond