39 lines
1.5 KiB
OCaml
39 lines
1.5 KiB
OCaml
(***********************************************************************)
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(* *)
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(* Objective Caml *)
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(* *)
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(* Damien Doligez, projet Para, INRIA Rocquencourt *)
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(* *)
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(* Copyright 1997 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 GNU Library General Public License. *)
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(* *)
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(***********************************************************************)
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(* $Id$ *)
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(* Module [Lazy]: deferred computations. *)
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type 'a status =
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| Delayed of (unit -> 'a)
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| Value of 'a
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| Exception of exn
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;;
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type 'a t = 'a status ref;;
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(* A value of type ['a Lazy.t] is a deferred computation (also called a
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suspension) that computes a result of type ['a]. The expression
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[lazy (expr)] returns a suspension that computes [expr].
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*)
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exception Undefined;;
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val force: 'a t -> 'a;;
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(* [Lazy.force x] computes the suspension [x] and returns its result.
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If the suspension was already computed, [Lazy.force x] returns the
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same value again. If it raised an exception, the same exception is
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raised again.
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Raise [Undefined] if the evaluation of the suspension requires its
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own result.
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*)
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