106 lines
2.9 KiB
OCaml
106 lines
2.9 KiB
OCaml
(***********************************************************************)
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(* *)
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(* Objective Caml *)
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(* *)
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(* Damien Doligez, projet Moscova, INRIA Rocquencourt *)
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(* *)
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(* Copyright 2002 Institut National de Recherche en Informatique et *)
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(* en Automatique. All rights reserved. This file is distributed *)
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(* under the terms of the Q Public License version 1.0. *)
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(* *)
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(***********************************************************************)
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(* $Id: hamming.ml 4303 2002-01-23 17:50:20Z doligez $ *)
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(* We cannot use bignums because we don't do custom runtimes, but
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int64 is a bit short, so we roll our own 37-digit numbers...
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*)
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let n0 = Int64.of_int 0;;
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let n1 = Int64.of_int 1;;
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let n2 = Int64.of_int 2;;
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let n3 = Int64.of_int 3;;
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let n5 = Int64.of_int 5;;
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let ( % ) = Int64.rem;;
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let ( * ) = Int64.mul;;
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let ( / ) = Int64.div;;
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let ( + ) = Int64.add;;
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let digit = Int64.of_string "1000000000000000000";;
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let mul n (pl, ph) = ((n * pl) % digit, n * ph + (n * pl) / digit);;
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let cmp (nl, nh) (pl, ph) =
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if nh < ph then -1
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else if nh > ph then 1
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else if nl < pl then -1
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else if nl > pl then 1
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else 0
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;;
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let x2 = fun p -> mul n2 p;;
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let x3 = fun p -> mul n3 p;;
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let x5 = fun p -> mul n5 p;;
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let nn1 = (n1, n0);;
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let pr (nl, nh) =
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if compare nh n0 = 0
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then Printf.printf "%Ld\n" nl
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else Printf.printf "%Ld%018Ld\n" nh nl
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;;
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(*
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(* bignum version *)
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open Num;;
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let nn1 = num_of_int 1;;
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let x2 = fun p -> (num_of_int 2) */ p;;
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let x3 = fun p -> (num_of_int 3) */ p;;
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let x5 = fun p -> (num_of_int 5) */ p;;
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let cmp n p = sign_num (n -/ p);;
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let pr n = Printf.printf "%s\n" (string_of_num n);;
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*)
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(* This is where the interesting stuff begins. *)
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open Lazy;;
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type 'a lcons = Cons of 'a * 'a lcons Lazy.t;;
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type 'a llist = 'a lcons Lazy.t;;
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let rec map f l =
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lazy (
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match force l with
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| Cons (x, ll) -> Cons (f x, map f ll)
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)
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;;
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let rec merge cmp l1 l2 =
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lazy (
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match force l1, force l2 with
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| Cons (x1, ll1), Cons (x2, ll2)
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-> let c = cmp x1 x2 in
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if c = 0
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then Cons (x1, merge cmp ll1 ll2)
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else if c < 0
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then Cons (x1, merge cmp ll1 l2)
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else Cons (x2, merge cmp l1 ll2)
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)
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;;
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let rec iter_interval f l (start, stop) =
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if stop = 0 then ()
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else match force l with
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| Cons (x, ll)
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-> if start <= 0 then f x;
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iter_interval f ll (start-1, stop-1)
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;;
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let rec hamming = lazy (Cons (nn1, merge cmp ham2 (merge cmp ham3 ham5)))
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and ham2 = lazy (force (map x2 hamming))
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and ham3 = lazy (force (map x3 hamming))
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and ham5 = lazy (force (map x5 hamming))
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;;
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iter_interval pr hamming (88000, 88100);;
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