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|
(* TEST *)
(* We cannot use bignums because we don't do custom runtimes, but
int64 is a bit short, so we roll our own 37-digit numbers...
*)
let n0 = Int64.of_int 0;;
let n1 = Int64.of_int 1;;
let n2 = Int64.of_int 2;;
let n3 = Int64.of_int 3;;
let n5 = Int64.of_int 5;;
let ( % ) = Int64.rem;;
let ( * ) = Int64.mul;;
let ( / ) = Int64.div;;
let ( + ) = Int64.add;;
let digit = Int64.of_string "1000000000000000000";;
let mul n (pl, ph) = ((n * pl) % digit, n * ph + (n * pl) / digit);;
let cmp (nl, nh) (pl, ph) =
if nh < ph then -1
else if nh > ph then 1
else if nl < pl then -1
else if nl > pl then 1
else 0
;;
let x2 = fun p -> mul n2 p;;
let x3 = fun p -> mul n3 p;;
let x5 = fun p -> mul n5 p;;
let nn1 = (n1, n0);;
let pr (nl, nh) =
if compare nh n0 = 0
then Printf.printf "%Ld\n" nl
else Printf.printf "%Ld%018Ld\n" nh nl
;;
(*
(* bignum version *)
open Num;;
let nn1 = num_of_int 1;;
let x2 = fun p -> (num_of_int 2) */ p;;
let x3 = fun p -> (num_of_int 3) */ p;;
let x5 = fun p -> (num_of_int 5) */ p;;
let cmp n p = sign_num (n -/ p);;
let pr n = Printf.printf "%s\n" (string_of_num n);;
*)
(* This is where the interesting stuff begins. *)
open Lazy;;
type 'a lcons = Cons of 'a * 'a lcons Lazy.t;;
type 'a llist = 'a lcons Lazy.t;;
let rec map f l =
lazy (
match force l with
| Cons (x, ll) -> Cons (f x, map f ll)
)
;;
let rec merge cmp l1 l2 =
lazy (
match force l1, force l2 with
| Cons (x1, ll1), Cons (x2, ll2)
-> let c = cmp x1 x2 in
if c = 0
then Cons (x1, merge cmp ll1 ll2)
else if c < 0
then Cons (x1, merge cmp ll1 l2)
else Cons (x2, merge cmp l1 ll2)
)
;;
let rec iter_interval f l (start, stop) =
if stop = 0 then ()
else match force l with
| Cons (x, ll)
-> if start <= 0 then f x;
iter_interval f ll (start-1, stop-1)
;;
let rec hamming = lazy (Cons (nn1, merge cmp ham2 (merge cmp ham3 ham5)))
and ham2 = lazy (force (map x2 hamming))
and ham3 = lazy (force (map x3 hamming))
and ham5 = lazy (force (map x5 hamming))
;;
iter_interval pr hamming (88000, 88100);;
|
