CCS

(* CCS: Calculus of Communicating Systems - vending machine example *)

(* A simple vending machine that accepts a coin then dispenses coffee or tea *)
VendingMachine = coin . (coffee . VendingMachine
                        + tea    . VendingMachine)

(* A customer who inserts a coin and then takes either coffee or tea *)
Customer = coin . (coffee . Customer
                 + tea    . Customer)

(* The complete system with coin and drink channels hidden *)
System = (VendingMachine | Customer) \ {coin, coffee, tea}