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