random: ajout get/set_state

git-svn-id: http://caml.inria.fr/svn/ocaml/trunk@3336 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02

2 files changed, 23 insertions, 1 deletions

diff --git a/stdlib/random.ml b/stdlib/random.ml
index 1cd238999..a3300ad4a 100644
--- a/stdlib/random.ml
+++ b/stdlib/random.ml
@@ -92,6 +92,18 @@ external random_seed: unit -> int = "sys_random_seed";;
 
 let self_init () = init (random_seed());;
 
+
+(* Manipulating the current state. *)
+
+type state = { state_array : int array; j : int };;
+
+let get_state () = { state_array = state; j = !j };;
+
+let set_state s =
+  Array.blit s.state_array 0 state 0 (Array.length state);
+  j := s.j;
+;;
+
 (********************
 
 (* Test functions.  Not included in the library.
diff --git a/stdlib/random.mli b/stdlib/random.mli
index 54ecd688a..2b00e58c3 100644
--- a/stdlib/random.mli
+++ b/stdlib/random.mli
@@ -12,7 +12,7 @@
 
 (* $Id$ *)
 
-(* Module [Random]: pseudo-random number generator *)
+(* Module [Random]: pseudo-random number generator (PRNG) *)
 
 val init : int -> unit
   (* Initialize the generator, using the argument as a seed.
@@ -34,3 +34,13 @@ val float : float -> float
      between 0 (inclusive) and [bound] (exclusive).  If [bound] is
      negative, the result is negative.  If [bound] is 0, the result
      is 0. *)
+
+type state;;
+  (* Values of this type are used to store the current state of the
+     generator. *)
+val get_state : unit -> state;;
+  (* Returns the current state of the generator.  This is useful for
+     checkpointing computations that use the PRNG. *)
+val set_state : state -> unit;;
+  (* Resets the state of the generator to some previous state returned by
+     [get_state]. *)