From daaf0904596d3f28f07f6273a9a1548f9b8b5a14 Mon Sep 17 00:00:00 2001
From: John Benediktsson <mrjbq7@gmail.com>
Date: Tue, 26 Mar 2013 16:24:45 -0700
Subject: [PATCH] hash-sets: faster intersect and diff, when both are
 hash-sets.

---
 core/hash-sets/hash-sets.factor | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/core/hash-sets/hash-sets.factor b/core/hash-sets/hash-sets.factor
index 9c40b4c2a2..2d79b9068d 100644
--- a/core/hash-sets/hash-sets.factor
+++ b/core/hash-sets/hash-sets.factor
@@ -149,7 +149,11 @@ INSTANCE: hash-set set
 
 PRIVATE>
 
-M: hash-set intersect (intersect) >hash-set ;
+M: hash-set intersect
+    over hash-set? [
+        small/large array/tester not-tombstones
+        filter >hash-set
+    ] [ (intersect) >hash-set ] if ;
 
 M: hash-set intersects?
     over hash-set? [
@@ -160,11 +164,13 @@ M: hash-set union
     over hash-set? [
         small/large [ array>> ] [ clone ] bi*
         [ [ adjoin ] curry each-member ] keep
-    ] [
-        (union) >hash-set
-    ] if ;
+    ] [ (union) >hash-set ] if ;
 
-M: hash-set diff (diff) >hash-set ;
+M: hash-set diff
+    over hash-set? [
+        array/tester [ not ] compose not-tombstones
+        filter >hash-set
+    ] [ (diff) >hash-set ] if ;
 
 M: hash-set subset?
     over hash-set? [