open Lib;;
let x = [| 1; 2 |] in
x.(0) <- 3;
if x.(0) <> 3 then raise Not_found
;;

(**
       0 CONSTINT 42
       2 PUSHACC0 
       3 MAKEBLOCK1 0
       5 POP 1
       7 SETGLOBAL Lib
       9 CONST2 
      10 PUSHCONST1 
      11 MAKEBLOCK2 0
      13 PUSHCONST3 
      14 PUSHCONST0 
      15 PUSHACC2 
      16 SETVECTITEM 
      17 CONST3 
      18 PUSHCONST0 
      19 PUSHACC2 
      20 GETVECTITEM 
      21 NEQ 
      22 BRANCHIFNOT 29
      24 GETGLOBAL Not_found
      26 MAKEBLOCK1 0
      28 RAISE 
      29 POP 1
      31 ATOM0 
      32 SETGLOBAL T131-setvectitem
      34 STOP 
**)