---

yaml
---
r: 42492
b: refs/heads/try
c: 1cfa01d
h: refs/heads/master
v: v3

Author: catamorphism

[refs]

@@ -2,7 +2,7 @@
 refs/heads/master: 19dfec2aaf746535de1521f68421f9980dbf25de
 refs/heads/snap-stage1: e33de59e47c5076a89eadeb38f4934f58a3618a6
 refs/heads/snap-stage3: 2f46b763da2c098913884f101b6d71d69af41b49
-refs/heads/try: ef0f71dc3fc8b203975c3da5230bed77becd0ee0
+refs/heads/try: 1cfa01decfbec571ac2d985339d6ebe0dbdf4a47
 refs/tags/release-0.1: 1f5c5126e96c79d22cb7862f75304136e204f105
 refs/heads/ndm: f3868061cd7988080c30d6d5bf352a5a5fe2460b
 refs/heads/try2: a810c03263670238bccd64cabb12a23a46e3a278

branches/try/src/libstd/bitv.rs

@@ -59,7 +59,7 @@ impl SmallBitv {
 
     #[inline(always)]
     fn difference(s: &SmallBitv, nbits: uint) -> bool {
-        self.bits_op(s.bits, nbits, |u1, u2| u1 ^ u2)
+        self.bits_op(s.bits, nbits, |u1, u2| u1 & !u2)
     }
 
     #[inline(always)]
@@ -180,10 +180,7 @@ impl BigBitv {
 
     #[inline(always)]
     fn difference(b: &BigBitv, nbits: uint) -> bool {
-        self.invert();
-        let b = self.intersect(b, nbits);
-        self.invert();
-        b
+        self.process(b, nbits, difference)
     }
 
     #[inline(always)]
@@ -567,6 +564,8 @@ pure fn lor(w0: uint, w1: uint) -> uint { return w0 | w1; }
 
 pure fn land(w0: uint, w1: uint) -> uint { return w0 & w1; }
 
+pure fn difference(w0: uint, w1: uint) -> uint { return w0 & !w1; }
+
 pure fn right(_w0: uint, w1: uint) -> uint { return w1; }
 
 impl Bitv: ops::Index<uint,bool> {
@@ -954,6 +953,34 @@ mod tests {
         let bools = ~[false, false, true, false, false, true, true, false];
         assert from_bytes([0b00100110]).to_bools() == bools;
     }
+
+    #[test]
+    fn test_small_difference() {
+      let b1 = Bitv(3, false);
+      let b2 = Bitv(3, false);
+      b1.set(0, true);
+      b1.set(1, true);
+      b2.set(1, true);
+      b2.set(2, true);
+      assert b1.difference(&b2);
+      assert b1[0];
+      assert !b1[1];
+      assert !b1[2];
+    }
+
+    #[test]
+    fn test_big_difference() {
+      let b1 = Bitv(100, false);
+      let b2 = Bitv(100, false);
+      b1.set(0, true);
+      b1.set(40, true);
+      b2.set(40, true);
+      b2.set(80, true);
+      assert b1.difference(&b2);
+      assert b1[0];
+      assert !b1[40];
+      assert !b1[80];
+    }
 }
 
 //