1 files changed, 122 insertions, 0 deletions
diff --git a/semestr-3/pf/lista6/lista6.ml b/semestr-3/pf/lista6/lista6.ml
new file mode 100644
index 0000000..686abe0
--- /dev/null
+++ b/semestr-3/pf/lista6/lista6.ml
@@ -0,0 +1,122 @@
+let rec fix f x = f (fix f) x
+
+let fib_f fib n =
+  if n <= 1 then n
+  else fib (n - 1) + fib (n - 2)
+
+let fib = fix fib_f
+
+(* Zadanie 1 *)
+
+let rec fix_with_limit limit f x = 
+  if limit > 0 then f (fix_with_limit (limit - 1) f) x
+  else failwith "Max recursion depth"
+
+let fix_memo f =
+  let ht = Hashtbl.create 10 in 
+  let rec fix ht f =
+    fun x -> try (Hashtbl.find ht x) with
+      | Not_found -> let result = f (fix ht f) x 
+        in Hashtbl.add ht x result ; result
+  in f (fix ht f)
+
+(* Zadanie 2 *)
+
+
+(* Zadanie 3 *)
+
+let create_counter () = 
+  let cnt = ref 0
+  in let next () =
+       let r = !cnt in 
+       cnt := r + 1;
+       r
+  in let reset () = 
+       cnt := 0
+  in (next, reset)
+
+let next, rest = create_counter ()
+
+(* Zadanie 4 *)
+
+type 'a stream = Stream of 'a * (unit -> 'a stream)
+
+let shd = function
+  | Stream (hd, tl) -> hd
+
+let stl = function
+  | Stream (hd, tl) -> tl ()
+
+let rec lfrom k = Stream (k, fun () -> lfrom (k + 1))
+
+let rec sfilter p (Stream (hd, tl)) = 
+  if p hd then (Stream (hd, fun () -> sfilter p (tl()))) else sfilter p (tl()) 
+
+let rec smap f (Stream (hd, tl))
+  = Stream (f hd, fun () -> smap f (tl()))
+
+let rec liebniz_gen k sign acc = 
+  Stream (4. *. (acc +. (sign *. (1.0 /.  k))), 
+          fun () -> liebniz_gen (k +. 2.) (-. sign) (acc +. (sign *. (1.0 /.  k))))
+
+let leibniz = liebniz_gen 1. 1. 0.
+
+let sum_pref n s = 
+  let rec iter acc n (Stream (hd, tl)) =
+    if n == 0 then acc else iter (acc +. hd) (n - 1) (tl())
+  in iter 0. n s
+
+let approx_leibniz n = sum_pref n leibniz
+
+let rec fold_three f s = 
+  let x1 = shd s in 
+  let xs = stl s in
+  let x2 = shd xs in
+  let x3 = shd (stl xs) in
+  Stream (f x1 x2 x3, fun () -> fold_three f xs)
+
+let rec stake n s = 
+  if n == 0 then shd s else stake (n - 1) (stl s)
+
+let euler_transform x y z = z -. (((y -. z) *. (y -. z))  /. (x -. (2.0 *. y) +. z))
+(* let rec s = fun () -> Stream (1., fun () -> Stream (3., fun () -> Stream (3.1, fun () -> fold_three euler_transform (s ())))) *)
+
+let pi_e = fold_three euler_transform leibniz 
+
+
+(* Zadanie 5 *)
+
+type 'a dllist = 'a dllist_data lazy_t
+and 'a dllist_data =
+  { prev : 'a dllist
+  ; elem : 'a
+  ; next : 'a dllist
+  }
+
+let prev = function
+  | lazy (dll) -> dll.prev
+
+let elem = function
+  | lazy (dll) -> dll.elem
+
+let next = function
+  | lazy (dll) -> dll.next
+
+
+let rec of_list xs =
+  let rec dll = List.map (fun x -> lazy {prev = get_previous dll x; elem = x; next = get_next dll x}) xs
+  in (List.hd (Lazy.force dll))
+and get_previous dll x =
+  let dll = Lazy.force dll in 
+  if (elem (List.hd dll)) == x then (List.hd (List.rev dll)) else
+    let rec iter prev xs = 
+      let y = List.hd xs 
+      in if (elem y) == x then prev else iter y (List.tl xs)
+    in iter (List.hd dll) (List.tl dll)
+and get_next dll x =
+  let dll = Lazy.force dll in
+  if (elem (List.hd (List.rev dll))) == x then List.hd dll else
+    let rec iter xs =
+      let y = List.hd xs
+      in if (elem y) == x then (List.hd (List.tl xs)) else iter (List.tl xs)
+    in iter (List.rev dll)