draft of Enum type (restartable generator a la Batteries)

containers.mllib

@@ -1,5 +1,6 @@
 Vector
 Deque
+Enum
 Graph
 Cache
 FlatHashtbl

enum.ml

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+(*
+Copyright (c) 2013, Simon Cruanes
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+Redistributions of source code must retain the above copyright notice, this
+list of conditions and the following disclaimer.  Redistributions in binary
+form must reproduce the above copyright notice, this list of conditions and the
+following disclaimer in the documentation and/or other materials provided with
+the distribution.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+*)
+
+(** {1 Consumable generators} *)
+
+exception EOG
+  (** End of Generation *)
+
+type 'a t = unit -> 'a generator
+  (** An enum is a generator of generators *)
+and 'a generator = unit -> 'a
+  (** A generator may be called several times, yielding the next value
+      each time. It raises EOG when it reaches the end. *)
+
+let start enum = enum ()
+
+let next gen = gen ()
+
+let junk gen = ignore (gen ())
+
+let fold f acc enum =
+  let rec fold acc gen =
+    let acc', stop =
+      try f acc (gen ()), true
+      with EOG -> acc, false in
+    if stop then acc' else fold acc' gen
+  in
+  fold acc (enum ())
+
+let iter f enum =
+  let rec iter gen =
+    let stop =
+      try f (gen ()); true
+      with EOG -> false in
+    if stop then () else iter gen
+  in
+  iter (enum ())
+
+let length enum =
+  fold (fun acc _ -> acc + 1) 0 enum
+              
+let map f enum =
+  (* another enum *)
+  fun () ->
+    let gen = enum () in
+    (* the mapped generator *)
+    fun () ->
+      try f (gen ())
+      with EOG -> raise EOG
+    
+let of_list l =
+  fun () ->
+    let l = ref l in
+    fun () ->
+      match !l with
+      | [] -> raise EOG
+      | x::l' -> l := l'; x
+
+let to_list enum =
+  let rec fold gen =
+    try (gen ()) :: fold gen
+    with EOG -> []
+  in fold (enum ())
+
+let to_rev_list enum =
+  let rec fold acc gen =
+    let acc', stop =
+      try gen () :: acc, true
+      with EOG -> acc, false
+    in if stop then acc' else fold acc' gen
+  in
+  fold [] (enum ())

enum.mli

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+(*
+Copyright (c) 2013, Simon Cruanes
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+Redistributions of source code must retain the above copyright notice, this
+list of conditions and the following disclaimer.  Redistributions in binary
+form must reproduce the above copyright notice, this list of conditions and the
+following disclaimer in the documentation and/or other materials provided with
+the distribution.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+*)
+
+(** {1 Consumable generators} *)
+
+(** This structure is inspired from Ocaml Batteries' BatEnum.t. It features
+    restartable generators. *)
+
+exception EOG
+  (** End of Generation *)
+
+type 'a t = unit -> 'a generator
+  (** An enum is a generator of generators *)
+and 'a generator = unit -> 'a
+  (** A generator may be called several times, yielding the next value
+      each time. It raises EOG when it reaches the end. *)
+
+val start : 'a t -> 'a generator
+  (** Create a new generator *)
+
+val next : 'a generator -> 'a
+  (** Get next element, or raise EOG *)
+
+val junk : 'a generator -> unit
+  (** Drop element *)
+
+val fold : ('b -> 'a -> 'b) -> 'b -> 'a t -> 'b
+  (** Fold on the generator *)
+
+val iter : ('a -> unit) -> 'a t -> unit
+  (** Iterate on the enum *)
+
+val length : _ t -> int
+  (** Length of an enum (linear time) *)
+
+val map : ('a -> 'b) -> 'a t -> 'b t
+  (** Lazy map *)
+
+val of_list : 'a list -> 'a t
+  (** Enumerate the list *)
+
+val to_list : 'a t -> 'a list
+  (** non tail-call trasnformation to list *)
+
+val to_rev_list : 'a t -> 'a list
+  (** Tail call conversion to list, in reverse order *)
+