karamaan/product-profunctors — pull request #9 by dbp (2014-10-10 16:43:22+00:00)
Title: add boilerplate for 19 and 20 elements, and missing defaults for 17 and 18

I added the boilerplate for 19/20 elements, and realizod, while doing that, that I had forgotten to the default instances for 17 and 18 (so this includes default stuff for 17-20).