lab 07

labs/07/exp.ml

@@ -0,0 +1,28 @@
+type 'a lazystream = Cons of 'a * 'a lazystream Lazy.t
+
+let rec from n = Cons (n, lazy (from (n +. 1.)))
+
+let rec take n (Cons (h, t)) =
+  if n <= 0 then []
+  else h :: take (n - 1) (Lazy.force t)
+
+let rec map f (Cons (h, t)) =
+  Cons (f h, lazy (map f (Lazy.force t)))
+
+let fact n =
+  let rec fact' acc i =
+    if i = 0. then acc
+    else fact' (i *. acc) (i -. 1.)
+  in
+  fact' 1. n;;
+
+let rec fold_left f acc l =
+  match l with
+  | [] -> acc
+  | a :: l' -> fold_left f (f acc a) l';;
+
+let exp_terms x = map (fun n -> (x**n) /. (fact n)) @@ from 0.;;
+
+let exp n x = fold_left (+.) 0. (take n @@ exp_terms x);;
+
+exp 20 1.1;;