POPL 2013 examples

[bennn]

The first (?) paper on choreographies has some interesting examples.
https://dl.acm.org/doi/10.1145/2480359.2429101

• Example 3 in section 2 has a Seller, two Buyers, and two Helpers (one for each buyer). The Buyer-Helper conversations are supposed to go out of order. Also, Buyer2's helper is supposed to send a result to the Seller to end the top-level choreography.
• Section 7 has one example of Audio Video Processing (AVP) and one with Open ID. Both seem decently realistic.

I started Example 3 in Chorex but got stuck deciding how to end the toplevel choreograpy:

defmodule C0 do
  import Chorex

  defchor [Buyer1, Buyer2, Seller] do
    def run(Buyer1.(book)) do
      Buyer1.(book) ~> Seller.(the_book)
      Seller.get_price(the_book) ~> Buyer1.(y1)
      Seller.get_price(the_book) ~> Buyer2.(z1)
      Buyer1.contrib(y1) ~> Buyer2.(z2)

      # ... start a sub-choreography. Don't care about the result.
      Buyer1.start_handler(0.5 * contrib(y1)) # result unused? paper is confusing

      # ... start a sub-chor ... and somehow this one has to communicate a result to Seller
      Buyer2.start_handler(0.5 * (z1 - z2), Seller)

      # TODO test that Buyer1 handler and Buyer2 handler can run out-of-order

    end
  end

end

Hope to pick this up again soon.