I've written a paper on contract checking. This is version 1.0:

 https://esapulkkinen.github.io/cifl-math-library/C++/contracts.pdf

This contains 33 pages and is quite dense in material, I've been
slowly adding material, but I thought since I have summer vacation now
it would be a good time to open the discussion on these.

This is intended for discussion, as some of the ideas are not yet good
enough for real proposal. It also includes lots of commentary on
various ideas and papers on contracts. I believe some of that
was already commented on in previous papers on the subject.

-- 
  Esa Pulkkinen <esa.pulkkinen_at_[hidden]>