Data commit

Task/Ackermann-function/OCaml/ackermann-function-1.ocaml

@@ -0,0 +1,4 @@
+let rec a m n =
+  if m=0 then (n+1) else
+  if n=0 then (a (m-1) 1) else
+  (a (m-1) (a m (n-1)))

Task/Ackermann-function/OCaml/ackermann-function-2.ocaml

@@ -0,0 +1,4 @@
+let rec a = function
+  | 0, n -> (n+1)
+  | m, 0 -> a(m-1, 1)
+  | m, n -> a(m-1, a(m, n-1))

Task/Ackermann-function/OCaml/ackermann-function-3.ocaml

@@ -0,0 +1,8 @@
+let h = Hashtbl.create 4001
+
+let a m n =
+  try Hashtbl.find h (m, n)
+  with Not_found ->
+    let res = a (m, n) in
+    Hashtbl.add h (m, n) res;
+    (res)

Task/Ackermann-function/OCaml/ackermann-function-4.ocaml

@@ -0,0 +1,7 @@
+let a m n =
+  for _m = 0 to m do
+    for _n = 0 to n do
+      ignore(a _m _n);
+    done;
+  done;
+  (a m n)

Task/Ackermann-function/OCaml/ackermann-function-5.ocaml

@@ -0,0 +1,11 @@
+open Big_int
+let one  = unit_big_int
+let zero = zero_big_int
+let succ = succ_big_int
+let pred = pred_big_int
+let eq = eq_big_int
+
+let rec a m n =
+  if eq m zero then (succ n) else
+  if eq n zero then (a (pred m) one) else
+  (a (pred m) (a m (pred n)))

Task/Ackermann-function/OCaml/ackermann-function-6.ocaml

@@ -0,0 +1,30 @@
+let rec find_option h v =
+  try Some(Hashtbl.find h v)
+  with Not_found -> None
+
+let rec a bounds caller todo m n =
+  match m, n with
+  | 0, n ->
+      let r = (n+1) in
+      ( match todo with
+        | [] -> r
+        | (m,n)::todo ->
+            List.iter (fun k ->
+              if not(Hashtbl.mem bounds k)
+              then Hashtbl.add bounds k r) caller;
+            a bounds [] todo m n )
+
+  | m, 0 ->
+      a bounds caller todo (m-1) 1
+
+  | m, n ->
+      match find_option bounds (m, n-1) with
+      | Some a_rec ->
+          let caller = (m,n)::caller in
+          a bounds caller todo (m-1) a_rec
+      | None ->
+          let todo = (m,n)::todo
+          and caller = [(m, n-1)] in
+          a bounds caller todo m (n-1)
+
+let a = a (Hashtbl.create 42 (* arbitrary *) ) [] [] ;;

Task/Ackermann-function/OCaml/ackermann-function-7.ocaml

@@ -0,0 +1,79 @@
+open Big_int
+let one  = unit_big_int
+let zero = zero_big_int
+let succ = succ_big_int
+let pred = pred_big_int
+let add = add_big_int
+let sub = sub_big_int
+let eq = eq_big_int
+let three = succ(succ one)
+let power = power_int_positive_big_int
+
+let eq2 (a1,a2) (b1,b2) =
+  (eq a1 b1) && (eq a2 b2)
+
+module H = Hashtbl.Make
+  (struct
+     type t = Big_int.big_int * Big_int.big_int
+     let equal = eq2
+     let hash (x,y) = Hashtbl.hash
+       (Big_int.string_of_big_int x ^ "," ^
+          Big_int.string_of_big_int y)
+       (* probably not a very good hash function *)
+   end)
+
+let rec find_option h v =
+  try Some (H.find h v)
+  with Not_found -> None
+
+let rec a bounds caller todo m n =
+  let may_tail r =
+    let k = (m,n) in
+    match todo with
+    | [] -> r
+    | (m,n)::todo ->
+        List.iter (fun k ->
+                     if not (H.mem bounds k)
+                     then H.add bounds k r) (k::caller);
+        a bounds [] todo m n
+  in
+  match m, n with
+  | m, n when eq m zero ->
+      let r = (succ n) in
+      may_tail r
+
+  | m, n when eq n zero ->
+      let caller = (m,n)::caller in
+      a bounds caller todo (pred m) one
+
+  | m, n when eq m three ->
+      let r = sub (power 2 (add n three)) three in
+      may_tail r
+
+  | m, n ->
+      match find_option bounds (m, pred n) with
+      | Some a_rec ->
+          let caller = (m,n)::caller in
+          a bounds caller todo (pred m) a_rec
+      | None ->
+          let todo = (m,n)::todo in
+          let caller = [(m, pred n)] in
+          a bounds caller todo m (pred n)
+
+let a = a (H.create 42 (* arbitrary *)) [] [] ;;
+
+let () =
+  let m, n =
+    try
+      big_int_of_string Sys.argv.(1),
+      big_int_of_string Sys.argv.(2)
+    with _ ->
+      Printf.eprintf "usage: %s <int> <int>\n" Sys.argv.(0);
+      exit 1
+  in
+  let r = a m n in
+  Printf.printf "(a %s %s) = %s\n"
+      (string_of_big_int m)
+      (string_of_big_int n)
+      (string_of_big_int r);
+;;