some small improvements to CCRandom

core/CCRandom.ml

@@ -41,6 +41,8 @@ let map f g st = f (g st)
 
 let (>|=) g f st = map f g st
 
+let delay f st = f () st
+
 let _choose_array a st =
   if Array.length a = 0 then invalid_arg "CCRandom.choose_array";
   a.(Random.State.int st (Array.length a))
@@ -69,6 +71,8 @@ let replicate n g st =
     if n = 0 then acc else aux (g st :: acc) (n-1)
   in aux [] n
 
+let list_seq l st = List.map (fun f -> f st) l
+
 exception SplitFail
 
 let _split i st =

core/CCRandom.mli

@@ -45,6 +45,21 @@ val map : ('a -> 'b) -> 'a t -> 'b t
 
 val (>|=) : 'a t -> ('a -> 'b) -> 'b t
 
+val delay : (unit -> 'a t) -> 'a t
+(** Delay evaluation. Useful for side-effectful generators that
+    need some code to run for every call.
+    Example:
+    {[
+    let gensym = let r = ref 0 in fun () -> incr r; !r ;;
+
+    delay (fun () ->
+      let name = gensym() in
+      small_int >>= fun i -> return (name,i)
+    )
+    ]}
+    @since NEXT_RELEASE
+*)
+
 val choose : 'a t list -> 'a option t
 (** Choose a generator within the list. *)
 
@@ -59,6 +74,12 @@ val choose_return : 'a list -> 'a t
     @raise Invalid_argument if the list is empty *)
 
 val replicate : int -> 'a t -> 'a list t
+(** [replace n g] makes a list of [n] elements which are all generated
+    randomly using [g] *)
+
+val list_seq : 'a t list -> 'a list t
+(** Build random lists from lists of random generators
+    @since NEXT_RELEASE *)
 
 val small_int : int t