From 32a59b7982cb1f9472e7d8c0ac675ab5ac22b893 Mon Sep 17 00:00:00 2001
From: Simon Cruanes <simon.cruanes.2007@m4x.org>
Date: Tue, 20 Aug 2013 12:15:35 +0200
Subject: [PATCH] added filter to leftistheap

---
 containers.mllib |  1 +
 leftistheap.ml   | 10 ++++++++++
 leftistheap.mli  |  3 +++
 3 files changed, 14 insertions(+)

diff --git a/containers.mllib b/containers.mllib
index fe678cdd..7741c056 100644
--- a/containers.mllib
+++ b/containers.mllib
@@ -24,3 +24,4 @@ RAL
 MultiSet
 UnionFind
 SmallSet
+Leftistheap
diff --git a/leftistheap.ml b/leftistheap.ml
index a5fc3e34..046079ba 100644
--- a/leftistheap.ml
+++ b/leftistheap.ml
@@ -79,6 +79,16 @@ let insert heap x =
   let tree = merge_tree heap.leq (Node (1, x, Empty, Empty)) heap.tree in
   { heap with tree; }
 
+let filter heap p =
+  let rec filter tree p = match tree with
+  | Empty -> Empty
+  | Node (_, x, l, r) when p x ->
+    merge_tree heap.leq (Node (1, x, Empty, Empty))
+      (merge_tree heap.leq (filter l p) (filter r p))
+  | Node (_, _, l, r) -> merge_tree heap.leq (filter l p) (filter r p)
+  in
+  { heap with tree = filter heap.tree p; }
+
 let find_min heap =
   match heap.tree with
   | Empty -> raise Not_found
diff --git a/leftistheap.mli b/leftistheap.mli
index 7565509a..a047e0bc 100644
--- a/leftistheap.mli
+++ b/leftistheap.mli
@@ -46,6 +46,9 @@ val merge : 'a t -> 'a t -> 'a t
 val insert : 'a t -> 'a -> 'a t
   (** Insert a value in the heap *)
 
+val filter : 'a t -> ('a -> bool) -> 'a t
+  (** Filter values, only retaining the ones that satisfy the predicate *)
+
 val find_min : 'a t -> 'a
   (** Find minimal element, or raise Not_found *)