resource users()
   import general_semaphore
   var S : cap general_semaphore
   var num_users : int := 5, nap_time : int := 4, init_val : int := 3
   var  run_time : int := 60
   getarg(1, num_users); getarg(2, nap_time); getarg(3, init_val)
   getarg(4, run_time)
   S := create general_semaphore("S", init_val)
   write(num_users, "users with nap_time=", nap_time, "initial value=",
      init_val, "and run_time=", run_time)

   process a_user(i := 1 to num_users)
      var napping : int
      do true ->
         napping := int(random(1000*nap_time))
         write("age()=", age(), "user", i, "napping for", napping)
         nap(napping)
         write("age()=", age(), "user", i, "doing a down")
         S.down()
         napping := int(random(1000*nap_time))
         write("age()=", age(), "after down, user", i, "napping for", napping)
         nap(napping)
         write("age()=", age(), "user", i, "doing an up")
         S.up()
      od
   end a_user

   nap(1000*run_time); write("must stop now"); stop
end users

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

% sr -o semaphores lock.sr general_semaphore.sr users.sr
lock.sr:
general_semaphore.sr:
users.sr:
lock.sr:
general_semaphore.sr:
users.sr:
linking:
% ./semaphores 5 4 2 7
a general semaphore named S with initial value 2 has been created
lockd: a lock named mutex has been created, initially locked? false
lockd: a lock named blocked has been created, initially locked? true
lockd: a lock named serial has been created, initially locked? false
5 users with nap_time= 4 initial value= 2 and run_time= 7
age()= 101 user 1 napping for 2394
age()= 105 user 2 napping for 151
age()= 108 user 3 napping for 2222
age()= 111 user 4 napping for 3573
age()= 114 user 5 napping for 3213
age()= 271 user 2 doing a down
DEBUG lockd: lock( serial )
DEBUG lockd: lock( mutex )
DEBUG down: for S count now is 1
DEBUG lockd: unlock( mutex )
DEBUG lockd: unlock( serial )
age()= 301 after down, user 2 napping for 1405
age()= 1718 user 2 doing an up
DEBUG lockd: lock( mutex )
DEBUG up: for S count now is 2
DEBUG lockd: unlock( mutex )
age()= 1730 user 2 napping for 813
age()= 2338 user 3 doing a down
DEBUG lockd: lock( serial )
DEBUG lockd: lock( mutex )
DEBUG down: for S count now is 1
DEBUG lockd: unlock( mutex )
DEBUG lockd: unlock( serial )
age()= 2351 after down, user 3 napping for 485
age()= 2508 user 1 doing a down
DEBUG lockd: lock( serial )
DEBUG lockd: lock( mutex )
DEBUG down: for S count now is 0
DEBUG lockd: unlock( mutex )
DEBUG lockd: unlock( serial )
age()= 2516 after down, user 1 napping for 2468
age()= 2548 user 2 doing a down
DEBUG lockd: lock( serial )
DEBUG lockd: lock( mutex )
DEBUG down: for S count now is -1
DEBUG lockd: unlock( mutex )
age()= 2838 user 3 doing an up
DEBUG lockd: lock( mutex )
DEBUG up: for S count now is 0
DEBUG lockd: unlock( blocked )
DEBUG lockd: lock( blocked )
DEBUG lockd: unlock( mutex )
DEBUG lockd: unlock( serial )
age()= 2847 user 3 napping for 1753
age()= 2849 after down, user 2 napping for 3566
age()= 3338 user 5 doing a down
DEBUG lockd: lock( serial )
DEBUG lockd: lock( mutex )
DEBUG down: for S count now is -1
DEBUG lockd: unlock( mutex )
age()= 3688 user 4 doing a down
age()= 4608 user 3 doing a down
age()= 4988 user 1 doing an up
DEBUG lockd: lock( mutex )
DEBUG up: for S count now is 0
DEBUG lockd: unlock( blocked )
DEBUG lockd: lock( blocked )
DEBUG lockd: unlock( mutex )
DEBUG lockd: unlock( serial )
DEBUG lockd: lock( serial )
age()= 4998 user 1 napping for 2565
age()= 5000 after down, user 5 napping for 2760
DEBUG lockd: lock( mutex )
DEBUG down: for S count now is -1
DEBUG lockd: unlock( mutex )
age()= 6418 user 2 doing an up
DEBUG lockd: lock( mutex )
DEBUG up: for S count now is 0
DEBUG lockd: unlock( blocked )
DEBUG lockd: lock( blocked )
DEBUG lockd: unlock( mutex )
DEBUG lockd: unlock( serial )
DEBUG lockd: lock( serial )
age()= 6429 user 2 napping for 853
age()= 6430 after down, user 4 napping for 2911
DEBUG lockd: lock( mutex )
DEBUG down: for S count now is -1
DEBUG lockd: unlock( mutex )
must stop now
                                              */