resource messages()
   op sum(p, q : int), answer(r : int)

   process process_a
      var z : int
      send sum(1, 2)
      receive answer(z)
      write("the sum of 1 and 2 is", z)
   end process_a

   process process_b
      var x, y : int
      receive sum(x, y)
      call answer(x+y)
   end process_b

end messages

/* ............... Example compile and run(s)

% sr -o messages messages.sr
% ./messages
the sum of 1 and 2 is 3
                                              */