unikernel/duniverse/seq/src/seq_redef.ml

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+(**************************************************************************)
+(*                                                                        *)
+(*                                 OCaml                                  *)
+(*                                                                        *)
+(*                 Simon Cruanes                                          *)
+(*                                                                        *)
+(*   Copyright 2017 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.          *)
+(*                                                                        *)
+(**************************************************************************)
+
+(* Module [Seq]: functional iterators *)
+
+type +'a node =
+  | Nil
+  | Cons of 'a * 'a t
+
+and 'a t = unit -> 'a node
+
+let empty () = Nil
+
+let return x () = Cons (x, empty)
+
+let rec map f seq () = match seq() with
+  | Nil -> Nil
+  | Cons (x, next) -> Cons (f x, map f next)
+
+let rec filter_map f seq () = match seq() with
+  | Nil -> Nil
+  | Cons (x, next) ->
+      match f x with
+        | None -> filter_map f next ()
+        | Some y -> Cons (y, filter_map f next)
+
+let rec filter f seq () = match seq() with
+  | Nil -> Nil
+  | Cons (x, next) ->
+      if f x
+      then Cons (x, filter f next)
+      else filter f next ()
+
+let rec flat_map f seq () = match seq () with
+  | Nil -> Nil
+  | Cons (x, next) ->
+    flat_map_app f (f x) next ()
+
+(* this is [append seq (flat_map f tail)] *)
+and flat_map_app f seq tail () = match seq () with
+  | Nil -> flat_map f tail ()
+  | Cons (x, next) ->
+    Cons (x, flat_map_app f next tail)
+
+let fold_left f acc seq =
+  let rec aux f acc seq = match seq () with
+    | Nil -> acc
+    | Cons (x, next) ->
+        let acc = f acc x in
+        aux f acc next
+  in
+  aux f acc seq
+
+let iter f seq =
+  let rec aux seq = match seq () with
+    | Nil -> ()
+    | Cons (x, next) ->
+        f x;
+        aux next
+  in
+  aux seq