1 files changed, 67 insertions, 0 deletions
diff --git a/ocaml/lib/noun.ml b/ocaml/lib/noun.ml
new file mode 100644
index 0000000..eb477db
--- /dev/null
+++ b/ocaml/lib/noun.ml
@@ -0,0 +1,67 @@
+type noun =
+  | Atom of Z.t
+  | Cell of noun * noun
+
+exception Exit
+
+let ensure_non_negative z =
+  if Z.sign z < 0 then raise Exit else z
+
+let atom z =
+  Atom (ensure_non_negative z)
+
+let atom_of_int n =
+  if n < 0 then raise Exit else Atom (Z.of_int n)
+
+(* Convert ASCII string to atom (bytes in little-endian order) *)
+let atom_of_string s =
+  if String.length s = 0 then atom Z.zero
+  else
+    let bytes = Bytes.of_string s in
+    atom (Z.of_bits (Bytes.to_string bytes))
+
+let cell h t = Cell (h, t)
+
+let zero = atom_of_int 0
+let one = atom_of_int 1
+
+let is_atom = function
+  | Atom _ -> true
+  | Cell _ -> false
+
+let is_cell = function
+  | Cell _ -> true
+  | Atom _ -> false
+
+let rec equal a b =
+  match a, b with
+  | Atom x, Atom y -> Z.equal x y
+  | Cell (ah, at), Cell (bh, bt) -> equal ah bh && equal at bt
+  | _ -> false
+
+let inc = function
+  | Atom z -> Atom (Z.succ z)
+  | Cell _ -> raise Exit
+
+let head = function
+  | Cell (h, _) -> h
+  | Atom _ -> raise Exit
+
+let tail = function
+  | Cell (_, t) -> t
+  | Atom _ -> raise Exit
+
+let rec slot axis noun =
+  if Z.equal axis Z.one then noun
+  else if Z.equal axis Z.zero then raise Exit
+  else
+    let bit = Z.testbit axis 0 in
+    let parent = Z.shift_right axis 1 in
+    let sub = slot parent noun in
+    if bit then tail sub else head sub
+
+let rec to_list noun =
+  match noun with
+  | Atom z when Z.equal z Z.zero -> []
+  | Cell (h, t) -> h :: to_list t
+  | _ -> raise Exit