open Reference;;


let prs s = print_string s; print_newline();;
let pri i = print_int i; print_newline();;
let pr s = print_string (s^": ");;


eval
  (fun memory ->
     let ref x = ref memory x in
       ref 0
         (fun p -> 
            pr "p"; pri (!p); 
            p := 3;
            pr "p"; pri (!p); 
            ref p
              (fun r ->
                 pr "(r)"; pri (!(!r));
                 ref (!p)
                   (fun q ->
                      pr "q"; pri (!q);
                      q := 2;
                      pr "q"; pri (!q);
                      pr "p"; pri (!p);
                      p := (!q + !p);
                      pr "p"; pri (!p);
                      pr "q"; pri (!q);
                      r := q;
                      pr "(r)"; pri (!(!r));
                   );
                 pr "(r)"; pri (!(!r));
              );
            
            ref "foo"
              (fun s ->
                 pr "s"; prs (!s)
              );
            pr "p"; pri (!p)
         )
  )
;;

print_int
  (eval (fun memory ->
        let ref x = ref memory x in
          ref 1 (fun r -> r := 3; !r + !r)))
;;
print_newline();; 

print_string "End of examples";;
print_newline();;