Move intersection above difference and symmetric_differance.

So all comes in the order union, intersection, difference and
symmetric_difference.

src/libcollections/bitv.rs

@@ -1124,8 +1124,8 @@ pub fn union<'a>(&'a self, other: &'a BitvSet) -> TwoBitPositions<'a> {
         }
     }
 
-    /// Iterator over each uint stored in the `self` setminus `other`.
-    /// See [difference_with](#method.difference_with) for an efficient in-place version.
+    /// Iterator over each uint stored in `self` intersect `other`.
+    /// See [intersect_with](#method.intersect_with) for an efficient in-place version.
     ///
     /// # Example
     ///
@@ -1136,32 +1136,25 @@ pub fn union<'a>(&'a self, other: &'a BitvSet) -> TwoBitPositions<'a> {
     /// let a = BitvSet::from_bitv(from_bytes([0b01101000]));
     /// let b = BitvSet::from_bitv(from_bytes([0b10100000]));
     ///
-    /// // Print 2, 4 in arbitrary order
-    /// for x in a.difference(&b) {
-    ///     println!("{}", x);
-    /// }
-    ///
-    /// // Note that difference is not symmetric,
-    /// // and `b - a` means something else.
-    /// // This prints 0
-    /// for x in b.difference(&a) {
+    /// // Print 2
+    /// for x in a.intersection(&b) {
     ///     println!("{}", x);
     /// }
     /// ```
     #[inline]
-    pub fn difference<'a>(&'a self, other: &'a BitvSet) -> TwoBitPositions<'a> {
+    pub fn intersection<'a>(&'a self, other: &'a BitvSet) -> Take<TwoBitPositions<'a>> {
+        let min = cmp::min(self.capacity(), other.capacity());
         TwoBitPositions {
             set: self,
             other: other,
-            merge: |w1, w2| w1 & !w2,
+            merge: |w1, w2| w1 & w2,
             current_word: 0,
             next_idx: 0
-        }
+        }.take(min)
     }
 
-    /// Iterator over each uint stored in the symmetric difference of `self` and `other`.
-    /// See [symmetric_difference_with](#method.symmetric_difference_with) for
-    /// an efficient in-place version.
+    /// Iterator over each uint stored in the `self` setminus `other`.
+    /// See [difference_with](#method.difference_with) for an efficient in-place version.
     ///
     /// # Example
     ///
@@ -1172,24 +1165,32 @@ pub fn difference<'a>(&'a self, other: &'a BitvSet) -> TwoBitPositions<'a> {
     /// let a = BitvSet::from_bitv(from_bytes([0b01101000]));
     /// let b = BitvSet::from_bitv(from_bytes([0b10100000]));
     ///
-    /// // Print 0, 1, 4 in arbitrary order
-    /// for x in a.symmetric_difference(&b) {
+    /// // Print 2, 4 in arbitrary order
+    /// for x in a.difference(&b) {
+    ///     println!("{}", x);
+    /// }
+    ///
+    /// // Note that difference is not symmetric,
+    /// // and `b - a` means something else.
+    /// // This prints 0
+    /// for x in b.difference(&a) {
     ///     println!("{}", x);
     /// }
     /// ```
     #[inline]
-    pub fn symmetric_difference<'a>(&'a self, other: &'a BitvSet) -> TwoBitPositions<'a> {
+    pub fn difference<'a>(&'a self, other: &'a BitvSet) -> TwoBitPositions<'a> {
         TwoBitPositions {
             set: self,
             other: other,
-            merge: |w1, w2| w1 ^ w2,
+            merge: |w1, w2| w1 & !w2,
             current_word: 0,
             next_idx: 0
         }
     }
 
-    /// Iterator over each uint stored in `self` intersect `other`.
-    /// See [intersect_with](#method.intersect_with) for an efficient in-place version.
+    /// Iterator over each uint stored in the symmetric difference of `self` and `other`.
+    /// See [symmetric_difference_with](#method.symmetric_difference_with) for
+    /// an efficient in-place version.
     ///
     /// # Example
     ///
@@ -1200,21 +1201,20 @@ pub fn symmetric_difference<'a>(&'a self, other: &'a BitvSet) -> TwoBitPositions
     /// let a = BitvSet::from_bitv(from_bytes([0b01101000]));
     /// let b = BitvSet::from_bitv(from_bytes([0b10100000]));
     ///
-    /// // Print 2
-    /// for x in a.intersection(&b) {
+    /// // Print 0, 1, 4 in arbitrary order
+    /// for x in a.symmetric_difference(&b) {
     ///     println!("{}", x);
     /// }
     /// ```
     #[inline]
-    pub fn intersection<'a>(&'a self, other: &'a BitvSet) -> Take<TwoBitPositions<'a>> {
-        let min = cmp::min(self.capacity(), other.capacity());
+    pub fn symmetric_difference<'a>(&'a self, other: &'a BitvSet) -> TwoBitPositions<'a> {
         TwoBitPositions {
             set: self,
             other: other,
-            merge: |w1, w2| w1 & w2,
+            merge: |w1, w2| w1 ^ w2,
             current_word: 0,
             next_idx: 0
-        }.take(min)
+        }
     }
 
     /// Union in-place with the specified other bit vector.