A polymorphic bloom filter in Ocaml implemented using Int32

Bloom32.ml

type 'a bloom32 = {
  size : int;
  bits : int32 array;
  hash_funs : ('a -> int) list
};;

let empty (n : int) (hfs : ('a -> int) list) = 
  let n_bits = if n mod 32 = 0 then n/32 else (n/32)+1 in
  {
  size = n;
  bits = Array.make n_bits 0l;
  hash_funs = hfs
}

let set_bit (ba : 'a bloom32) (n : int) =
  let array_index = n/32 in
  let bit_index = n mod 32 in
  ba.bits.(array_index) <- Int32.logor ba.bits.(array_index) (Int32.shift_left 0b1l bit_index)

let add (ba : 'a bloom32) (e : 'a) =
  ignore (List.map (fun f -> set_bit ba (f e)) ba.hash_funs)

let is_bit_set (ba : 'a bloom32) (n : int) =
  let array_index = n/32 in
  let bit_index = n mod 32 in
  Int32.logand ba.bits.(array_index) (Int32.shift_left 0b1l bit_index) <> 0l;;

let query (ba : 'a bloom32) (e : 'a) =
  List.exists (fun f -> is_bit_set ba (f e)) ba.hash_funs;;