unikernel/duniverse/ocaml-caqti/caqti/lib-platform/heap.ml

@@ -0,0 +1,61 @@
+(* Copyright (C) 2014--2016  Petter A. Urkedal <paurkedal@gmail.com>
+ *
+ * This library is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or (at your
+ * option) any later version, with the LGPL-3.0 Linking Exception.
+ *
+ * This library is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
+ * License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * and the LGPL-3.0 Linking Exception along with this library.  If not, see
+ * <http://www.gnu.org/licenses/> and <https://spdx.org>, respectively.
+ *)
+
+module type S = sig
+  type elt
+  type t
+
+  val empty : t
+  val is_empty : t -> bool
+  val card : t -> int
+  val push : elt -> t -> t
+  val merge : t -> t -> t
+  val pop_e : t -> elt * t
+end
+
+module Make (Elt : Set.OrderedType) = struct
+
+  type elt = Elt.t
+  type t = O | Y of int * elt * t * t
+
+  let empty = O
+
+  let is_empty h = h = O
+
+  let card = function
+    | O -> 0
+    | Y (n, _, _, _) -> n
+
+  let rec push e' = function
+    | O -> Y (1, e', O, O)
+    | Y (n, e, hL, hR) ->
+      let e_min, e_max = if Elt.compare e' e < 0 then e', e else e, e' in
+      if card hL < card hR then Y (n + 1, e_min, push e_max hL, hR)
+                           else Y (n + 1, e_min, hL, push e_max hR)
+
+  let rec merge hL hR =
+    match hL, hR with
+    | O, h | h, O -> h
+    | Y (nL, eL, hA, hB), Y (nR, eR, hC, hD) ->
+      if Elt.compare eL eR < 0 then Y (nL + nR, eL, merge hA hB, hR)
+                               else Y (nL + nR, eR, hL, merge hC hD)
+
+  let pop_e = function
+    | O -> invalid_arg "Caqti_heap.pop_e: Empty heap."
+    | Y (_, e, hL, hR) -> e, merge hL hR
+
+end