55 lines
1.9 KiB
OCaml
55 lines
1.9 KiB
OCaml
(***********************************************************************)
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(* *)
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(* Objective Caml *)
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(* *)
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(* Xavier Leroy, projet Cristal, INRIA Rocquencourt *)
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(* *)
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(* Copyright 1996 Institut National de Recherche en Informatique et *)
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(* Automatique. Distributed only by permission. *)
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(* *)
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(***********************************************************************)
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(* $Id$ *)
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(* lsb is the least significant bit of the native int (0 <= lsb <= 1)
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msw is the remaining 31 or 63 most significant bits. *)
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type t = { msw: int; lsb: int }
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let from i = { msw = i asr 1; lsb = i land 1 }
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let to_int n = (n.msw lsl 1) lor n.lsb
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let add n1 n2 =
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let s = n1.lsb + n2.lsb in
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{ msw = n1.msw + n2.msw + s asr 1; lsb = s land 1 }
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let sub n1 n2 =
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let d = n1.lsb - n2.lsb in
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{ msw = n1.msw - n2.msw + d asr 1; lsb = d land 1 }
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let shift n s =
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if s = 0 then n else
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if s > 0 then
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{ msw = (n.msw lsl s) lor (n.lsb lsl (s-1)); lsb = 0 }
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else
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{ msw = n.msw asr (-s); lsb = (n.msw asr (-s - 1)) land 1 }
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let sign n =
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if n.msw < 0 then -1 else
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if n.msw = 0 && n.lsb = 0 then 0 else 1
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let compare n1 n2 = sign(sub n1 n2)
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let cmp n1 i2 = compare n1 (from i2)
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let to_string n =
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let a = if n.msw >= 0 then n else sub (from 0) n in
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let (q, r) =
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(* Watch out for the case n.msw = min_int, in which case a.msw < 0 *)
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if a.msw <> min_int
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then (a.msw / 5, a.msw mod 5)
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else (max_int / 5, max_int mod 5 + 1) in
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(if n.msw >= 0 then "" else "-") ^
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(if q > 0 then string_of_int q else "") ^
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string_of_int (r * 2 + a.lsb)
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