/usr/lib/ocaml/camlinternalLazy.ml is in ocaml-nox 4.05.0-10ubuntu1.
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(* *)
(* OCaml *)
(* *)
(* Damien Doligez, projet Para, INRIA Rocquencourt *)
(* *)
(* Copyright 1997 Institut National de Recherche en Informatique et *)
(* en Automatique. *)
(* *)
(* All rights reserved. This file is distributed under the terms of *)
(* the GNU Lesser General Public License version 2.1, with the *)
(* special exception on linking described in the file LICENSE. *)
(* *)
(**************************************************************************)
(* Internals of forcing lazy values. *)
exception Undefined
let raise_undefined = Obj.repr (fun () -> raise Undefined)
(* Assume [blk] is a block with tag lazy *)
let force_lazy_block (blk : 'arg lazy_t) =
let closure = (Obj.obj (Obj.field (Obj.repr blk) 0) : unit -> 'arg) in
Obj.set_field (Obj.repr blk) 0 raise_undefined;
try
let result = closure () in
(* do set_field BEFORE set_tag *)
Obj.set_field (Obj.repr blk) 0 (Obj.repr result);
Obj.set_tag (Obj.repr blk) Obj.forward_tag;
result
with e ->
Obj.set_field (Obj.repr blk) 0 (Obj.repr (fun () -> raise e));
raise e
(* Assume [blk] is a block with tag lazy *)
let force_val_lazy_block (blk : 'arg lazy_t) =
let closure = (Obj.obj (Obj.field (Obj.repr blk) 0) : unit -> 'arg) in
Obj.set_field (Obj.repr blk) 0 raise_undefined;
let result = closure () in
(* do set_field BEFORE set_tag *)
Obj.set_field (Obj.repr blk) 0 (Obj.repr result);
Obj.set_tag (Obj.repr blk) (Obj.forward_tag);
result
(* [force] is not used, since [Lazy.force] is declared as a primitive
whose code inlines the tag tests of its argument. This function is
here for the sake of completeness, and for debugging purpose. *)
let force (lzv : 'arg lazy_t) =
let x = Obj.repr lzv in
let t = Obj.tag x in
if t = Obj.forward_tag then (Obj.obj (Obj.field x 0) : 'arg) else
if t <> Obj.lazy_tag then (Obj.obj x : 'arg)
else force_lazy_block lzv
let force_val (lzv : 'arg lazy_t) =
let x = Obj.repr lzv in
let t = Obj.tag x in
if t = Obj.forward_tag then (Obj.obj (Obj.field x 0) : 'arg) else
if t <> Obj.lazy_tag then (Obj.obj x : 'arg)
else force_val_lazy_block lzv
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