(\x. 
                spawn (rendezvous 1 ; print *x ; rendezvous 2) ;
                spawn (rendezvous 3 ; print *x ; rendezvous 4) ;
                print *x ;
                *x := (*x) + 1 ;
                rendezvous 1 ;  rendezvous 2 ;
                *x := (*x) + 1 ;
                rendezvous 3 ; rendezvous 4) (ref 1)
