From 4957e343f5543bf8be6f5a02bfff5861385647f5 Mon Sep 17 00:00:00 2001
From: Daniel Micay <danielmicay@gmail.com>
Date: Sun, 9 Dec 2012 20:02:33 -0500
Subject: [PATCH 01/11] add priority queue implementation (binary heap)

---
 src/libstd/priority_queue.rs | 253 +++++++++++++++++++++++++++++++++++
 src/libstd/std.rc            |   1 +
 2 files changed, 254 insertions(+)
 create mode 100644 src/libstd/priority_queue.rs

diff --git a/src/libstd/priority_queue.rs b/src/libstd/priority_queue.rs
new file mode 100644
index 0000000000000..c744ba1ca5cea
--- /dev/null
+++ b/src/libstd/priority_queue.rs
@@ -0,0 +1,253 @@
+
+/// A priority queue implemented with a binary heap
+use core::cmp::Ord;
+
+pub struct PriorityQueue <T: Copy Ord>{
+    priv data: ~[T],
+}
+
+impl <T: Copy Ord> PriorityQueue<T> {
+    /// Returns the greatest item in the queue - fails if empty
+    pure fn top(&self) -> T { self.data[0] }
+
+    /// Returns the greatest item in the queue - None if empty
+    pure fn maybe_top(&self) -> Option<T> {
+        if self.is_empty() { None } else { Some(self.top()) }
+    }
+
+    /// Returns the length of the queue
+    pure fn len(&self) -> uint { self.data.len() }
+
+    /// Returns true if a queue contains no elements
+    pure fn is_empty(&self) -> bool { self.data.is_empty() }
+
+    /// Returns true if a queue contains some elements
+    pure fn is_not_empty(&self) -> bool { self.data.is_not_empty() }
+
+    /// Returns the number of elements the queue can hold without reallocating
+    pure fn capacity(&self) -> uint { vec::capacity(&self.data) }
+
+    fn reserve(&mut self, n: uint) { vec::reserve(&mut self.data, n) }
+
+    fn reserve_at_least(&mut self, n: uint) {
+        vec::reserve_at_least(&mut self.data, n)
+    }
+
+    /// Drop all items from the queue
+    fn clear(&mut self) { self.data.truncate(0) }
+
+    /// Pop the greatest item from the queue - fails if empty
+    fn pop(&mut self) -> T {
+        let last = self.data.pop();
+        if self.is_not_empty() {
+            let ret = self.data[0];
+            self.data[0] = last;
+            self.siftup(0);
+            ret
+        } else { last }
+    }
+
+    /// Pop the greatest item from the queue - None if empty
+    fn maybe_pop(&mut self) -> Option<T> {
+        if self.is_empty() { None } else { Some(self.pop()) }
+    }
+
+    /// Push an item onto the queue
+    fn push(&mut self, item: T) {
+        self.data.push(item);
+        self.siftdown(0, self.len() - 1);
+    }
+
+    /// Optimized version of a push followed by a pop
+    fn push_pop(&mut self, item: T) -> T {
+        let mut item = item;
+        if self.is_not_empty() && self.data[0] > item {
+            item <-> self.data[0];
+            self.siftup(0);
+        }
+        item
+    }
+
+    /// Optimized version of a pop followed by a push - fails if empty
+    fn replace(&mut self, item: T) -> T {
+        let ret = self.data[0];
+        self.data[0] = item;
+        self.siftup(0);
+        ret
+    }
+
+    priv fn siftdown(&mut self, startpos: uint, pos: uint) {
+        let mut pos = pos;
+        let newitem = self.data[pos];
+
+        while pos > startpos {
+            let parentpos = (pos - 1) >> 1;
+            let parent = self.data[parentpos];
+            if newitem > parent {
+                self.data[pos] = parent;
+                pos = parentpos;
+                loop
+            }
+            break
+        }
+        self.data[pos] = newitem;
+    }
+
+    priv fn siftup_range(&mut self, pos: uint, endpos: uint) {
+        let mut pos = pos;
+        let startpos = pos;
+        let newitem = self.data[pos];
+
+        let mut childpos = 2 * pos + 1;
+        while childpos < endpos {
+            let rightpos = childpos + 1;
+            if rightpos < endpos &&
+                   !(self.data[childpos] > self.data[rightpos]) {
+                childpos = rightpos;
+            }
+            self.data[pos] = self.data[childpos];
+            pos = childpos;
+            childpos = 2 * pos + 1;
+        }
+        self.data[pos] = newitem;
+        self.siftdown(startpos, pos);
+    }
+
+    priv fn siftup(&mut self, pos: uint) {
+        self.siftup_range(pos, self.len());
+    }
+}
+
+/// Consume the PriorityQueue and return the underlying vector
+pub pure fn to_vec<T: Copy Ord>(q: PriorityQueue<T>) -> ~[T] {
+    let PriorityQueue{data: v} = q;
+    v
+}
+
+/// Consume the PriorityQueue and return a vector in sorted (ascending) order
+pub pure fn to_sorted_vec<T: Copy Ord>(q: PriorityQueue<T>) -> ~[T] {
+    let mut q = q;
+    let mut end = q.len() - 1;
+    while end > 0 {
+        q.data[end] <-> q.data[0];
+        end -= 1;
+        unsafe { q.siftup_range(0, end) } // purity-checking workaround
+    }
+    to_vec(q)
+}
+
+pub pure fn from_vec<T: Copy Ord>(xs: ~[T]) -> PriorityQueue<T> {
+    let mut q = PriorityQueue{data: xs,};
+    let mut n = q.len() / 2;
+    while n > 0 {
+        n -= 1;
+        unsafe { q.siftup(n) }; // purity-checking workaround
+    }
+    q
+}
+
+#[cfg(test)]
+mod tests {
+    use sort::merge_sort;
+    use core::cmp::le;
+
+    #[test]
+    fn test_top_and_pop() {
+        let data = ~[2, 4, 6, 2, 1, 8, 10, 3, 5, 7, 0, 9, 1];
+        let mut sorted = merge_sort(data, le);
+        let mut heap = from_vec(data);
+        while heap.is_not_empty() {
+            assert heap.top() == sorted.last();
+            assert heap.pop() == sorted.pop();
+        }
+    }
+
+    #[test]
+    fn test_push() {
+        let mut heap = from_vec(~[2, 4, 9]);
+        assert heap.len() == 3;
+        assert heap.top() == 9;
+        heap.push(11);
+        assert heap.len() == 4;
+        assert heap.top() == 11;
+        heap.push(5);
+        assert heap.len() == 5;
+        assert heap.top() == 11;
+        heap.push(27);
+        assert heap.len() == 6;
+        assert heap.top() == 27;
+        heap.push(3);
+        assert heap.len() == 7;
+        assert heap.top() == 27;
+        heap.push(103);
+        assert heap.len() == 8;
+        assert heap.top() == 103;
+    }
+
+    #[test]
+    fn test_push_pop() {
+        let mut heap = from_vec(~[5, 5, 2, 1, 3]);
+        assert heap.len() == 5;
+        assert heap.push_pop(6) == 6;
+        assert heap.len() == 5;
+        assert heap.push_pop(0) == 5;
+        assert heap.len() == 5;
+        assert heap.push_pop(4) == 5;
+        assert heap.len() == 5;
+        assert heap.push_pop(1) == 4;
+        assert heap.len() == 5;
+    }
+
+    #[test]
+    fn test_replace() {
+        let mut heap = from_vec(~[5, 5, 2, 1, 3]);
+        assert heap.len() == 5;
+        assert heap.replace(6) == 5;
+        assert heap.len() == 5;
+        assert heap.replace(0) == 6;
+        assert heap.len() == 5;
+        assert heap.replace(4) == 5;
+        assert heap.len() == 5;
+        assert heap.replace(1) == 4;
+        assert heap.len() == 5;
+    }
+
+    #[test]
+    fn test_to_sorted_vec() {
+        let data = ~[2, 4, 6, 2, 1, 8, 10, 3, 5, 7, 0, 9, 1];
+        assert to_sorted_vec(from_vec(data)) == merge_sort(data, le);
+    }
+
+    #[test]
+    #[should_fail]
+    fn test_empty_pop() { let mut heap = from_vec::<int>(~[]); heap.pop(); }
+
+    #[test]
+    fn test_empty_maybe_pop() {
+        let mut heap = from_vec::<int>(~[]);
+        assert heap.maybe_pop().is_none();
+    }
+
+    #[test]
+    #[should_fail]
+    fn test_empty_top() { from_vec::<int>(~[]).top(); }
+
+    #[test]
+    fn test_empty_maybe_top() {
+        assert from_vec::<int>(~[]).maybe_top().is_none();
+    }
+
+    #[test]
+    #[should_fail]
+    fn test_empty_replace() {
+        let mut heap = from_vec::<int>(~[]);
+        heap.replace(5);
+    }
+
+    #[test]
+    fn test_to_vec() {
+        let data = ~[1, 3, 5, 7, 9, 2, 4, 6, 8, 0];
+        let heap = from_vec(copy data);
+        assert merge_sort(to_vec(heap), le) == merge_sort(data, le);
+    }
+}
diff --git a/src/libstd/std.rc b/src/libstd/std.rc
index 65916aa599274..f5363ca23c503 100644
--- a/src/libstd/std.rc
+++ b/src/libstd/std.rc
@@ -73,6 +73,7 @@ pub mod deque;
 pub mod fun_treemap;
 pub mod list;
 pub mod map;
+pub mod priority_queue;
 pub mod rope;
 pub mod smallintmap;
 pub mod sort;

From c48ba6304b4b86a69af17243379b5780c42bc4a2 Mon Sep 17 00:00:00 2001
From: Daniel Micay <danielmicay@gmail.com>
Date: Mon, 10 Dec 2012 15:36:01 -0500
Subject: [PATCH 02/11] priority_queue: make to_vec/to_sorted_vec methods

---
 src/libstd/priority_queue.rs | 37 +++++++++++++++++-------------------
 1 file changed, 17 insertions(+), 20 deletions(-)

diff --git a/src/libstd/priority_queue.rs b/src/libstd/priority_queue.rs
index c744ba1ca5cea..31d6e04ae6267 100644
--- a/src/libstd/priority_queue.rs
+++ b/src/libstd/priority_queue.rs
@@ -76,6 +76,21 @@ impl <T: Copy Ord> PriorityQueue<T> {
         ret
     }
 
+    /// Consume the PriorityQueue and return the underlying vector
+    pure fn to_vec(self) -> ~[T] { let PriorityQueue{data: v} = self; v }
+
+    /// Consume the PriorityQueue and return a vector in sorted (ascending) order
+    pure fn to_sorted_vec(self) -> ~[T] {
+        let mut q = self;
+        let mut end = q.len() - 1;
+        while end > 0 {
+            q.data[end] <-> q.data[0];
+            end -= 1;
+            unsafe { q.siftup_range(0, end) } // purity-checking workaround
+        }
+        q.to_vec()
+    }
+
     priv fn siftdown(&mut self, startpos: uint, pos: uint) {
         let mut pos = pos;
         let newitem = self.data[pos];
@@ -118,24 +133,6 @@ impl <T: Copy Ord> PriorityQueue<T> {
     }
 }
 
-/// Consume the PriorityQueue and return the underlying vector
-pub pure fn to_vec<T: Copy Ord>(q: PriorityQueue<T>) -> ~[T] {
-    let PriorityQueue{data: v} = q;
-    v
-}
-
-/// Consume the PriorityQueue and return a vector in sorted (ascending) order
-pub pure fn to_sorted_vec<T: Copy Ord>(q: PriorityQueue<T>) -> ~[T] {
-    let mut q = q;
-    let mut end = q.len() - 1;
-    while end > 0 {
-        q.data[end] <-> q.data[0];
-        end -= 1;
-        unsafe { q.siftup_range(0, end) } // purity-checking workaround
-    }
-    to_vec(q)
-}
-
 pub pure fn from_vec<T: Copy Ord>(xs: ~[T]) -> PriorityQueue<T> {
     let mut q = PriorityQueue{data: xs,};
     let mut n = q.len() / 2;
@@ -215,7 +212,7 @@ mod tests {
     #[test]
     fn test_to_sorted_vec() {
         let data = ~[2, 4, 6, 2, 1, 8, 10, 3, 5, 7, 0, 9, 1];
-        assert to_sorted_vec(from_vec(data)) == merge_sort(data, le);
+        assert from_vec(data).to_sorted_vec() == merge_sort(data, le);
     }
 
     #[test]
@@ -248,6 +245,6 @@ mod tests {
     fn test_to_vec() {
         let data = ~[1, 3, 5, 7, 9, 2, 4, 6, 8, 0];
         let heap = from_vec(copy data);
-        assert merge_sort(to_vec(heap), le) == merge_sort(data, le);
+        assert merge_sort(heap.to_vec(), le) == merge_sort(data, le);
     }
 }

From d89da37b0a8d7505ea5d9ce6cb74daea72142efc Mon Sep 17 00:00:00 2001
From: Daniel Micay <danielmicay@gmail.com>
Date: Mon, 10 Dec 2012 15:46:41 -0500
Subject: [PATCH 03/11] priority_queue: make from_vec a static method

---
 src/libstd/priority_queue.rs | 21 +++++++++++----------
 1 file changed, 11 insertions(+), 10 deletions(-)

diff --git a/src/libstd/priority_queue.rs b/src/libstd/priority_queue.rs
index 31d6e04ae6267..b92f5f57a5ff8 100644
--- a/src/libstd/priority_queue.rs
+++ b/src/libstd/priority_queue.rs
@@ -91,6 +91,16 @@ impl <T: Copy Ord> PriorityQueue<T> {
         q.to_vec()
     }
 
+    static pub pure fn from_vec(xs: ~[T]) -> PriorityQueue<T> {
+        let mut q = PriorityQueue{data: xs,};
+        let mut n = q.len() / 2;
+        while n > 0 {
+            n -= 1;
+            unsafe { q.siftup(n) }; // purity-checking workaround
+        }
+        q
+    }
+
     priv fn siftdown(&mut self, startpos: uint, pos: uint) {
         let mut pos = pos;
         let newitem = self.data[pos];
@@ -133,20 +143,11 @@ impl <T: Copy Ord> PriorityQueue<T> {
     }
 }
 
-pub pure fn from_vec<T: Copy Ord>(xs: ~[T]) -> PriorityQueue<T> {
-    let mut q = PriorityQueue{data: xs,};
-    let mut n = q.len() / 2;
-    while n > 0 {
-        n -= 1;
-        unsafe { q.siftup(n) }; // purity-checking workaround
-    }
-    q
-}
-
 #[cfg(test)]
 mod tests {
     use sort::merge_sort;
     use core::cmp::le;
+    use PriorityQueue::from_vec;
 
     #[test]
     fn test_top_and_pop() {

From 99119096ef0b195c8a531e9d28025cec51850911 Mon Sep 17 00:00:00 2001
From: Daniel Micay <danielmicay@gmail.com>
Date: Tue, 11 Dec 2012 09:47:36 -0500
Subject: [PATCH 04/11] priority_queue: replace some copies with swaps

---
 src/libstd/priority_queue.rs | 16 ++++++----------
 1 file changed, 6 insertions(+), 10 deletions(-)

diff --git a/src/libstd/priority_queue.rs b/src/libstd/priority_queue.rs
index b92f5f57a5ff8..ab274970ab3c3 100644
--- a/src/libstd/priority_queue.rs
+++ b/src/libstd/priority_queue.rs
@@ -38,13 +38,9 @@ impl <T: Copy Ord> PriorityQueue<T> {
 
     /// Pop the greatest item from the queue - fails if empty
     fn pop(&mut self) -> T {
-        let last = self.data.pop();
-        if self.is_not_empty() {
-            let ret = self.data[0];
-            self.data[0] = last;
-            self.siftup(0);
-            ret
-        } else { last }
+        let mut item = self.data.pop();
+        if self.is_not_empty() { item <-> self.data[0]; self.siftup(0); }
+        item
     }
 
     /// Pop the greatest item from the queue - None if empty
@@ -70,10 +66,10 @@ impl <T: Copy Ord> PriorityQueue<T> {
 
     /// Optimized version of a pop followed by a push - fails if empty
     fn replace(&mut self, item: T) -> T {
-        let ret = self.data[0];
-        self.data[0] = item;
+        let mut item = item;
+        item <-> self.data[0];
         self.siftup(0);
-        ret
+        item
     }
 
     /// Consume the PriorityQueue and return the underlying vector

From 45119c38acd442d4a7c56ef424888705e4f0124e Mon Sep 17 00:00:00 2001
From: Daniel Micay <danielmicay@gmail.com>
Date: Tue, 11 Dec 2012 10:57:37 -0500
Subject: [PATCH 05/11] priority_queue: fix to_sorted_vec off-by-one error

---
 src/libstd/priority_queue.rs | 36 +++++++++++++++++++++++-------------
 1 file changed, 23 insertions(+), 13 deletions(-)

diff --git a/src/libstd/priority_queue.rs b/src/libstd/priority_queue.rs
index ab274970ab3c3..35d238b4d7cc1 100644
--- a/src/libstd/priority_queue.rs
+++ b/src/libstd/priority_queue.rs
@@ -78,10 +78,10 @@ impl <T: Copy Ord> PriorityQueue<T> {
     /// Consume the PriorityQueue and return a vector in sorted (ascending) order
     pure fn to_sorted_vec(self) -> ~[T] {
         let mut q = self;
-        let mut end = q.len() - 1;
-        while end > 0 {
-            q.data[end] <-> q.data[0];
+        let mut end = q.len();
+        while end > 1 {
             end -= 1;
+            q.data[end] <-> q.data[0];
             unsafe { q.siftup_range(0, end) } // purity-checking workaround
         }
         q.to_vec()
@@ -206,10 +206,27 @@ mod tests {
         assert heap.len() == 5;
     }
 
+    fn check_to_vec(data: ~[int]) {
+        let heap = from_vec(data);
+        assert merge_sort(heap.to_vec(), le) == merge_sort(data, le);
+        assert heap.to_sorted_vec() == merge_sort(data, le);
+    }
+
     #[test]
-    fn test_to_sorted_vec() {
-        let data = ~[2, 4, 6, 2, 1, 8, 10, 3, 5, 7, 0, 9, 1];
-        assert from_vec(data).to_sorted_vec() == merge_sort(data, le);
+    fn test_to_vec() {
+        check_to_vec(~[]);
+        check_to_vec(~[5]);
+        check_to_vec(~[3, 2]);
+        check_to_vec(~[2, 3]);
+        check_to_vec(~[5, 1, 2]);
+        check_to_vec(~[1, 100, 2, 3]);
+        check_to_vec(~[1, 3, 5, 7, 9, 2, 4, 6, 8, 0]);
+        check_to_vec(~[2, 4, 6, 2, 1, 8, 10, 3, 5, 7, 0, 9, 1]);
+        check_to_vec(~[9, 11, 9, 9, 9, 9, 11, 2, 3, 4, 11, 9, 0, 0, 0, 0]);
+        check_to_vec(~[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]);
+        check_to_vec(~[10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0]);
+        check_to_vec(~[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 0, 0, 1, 2]);
+        check_to_vec(~[5, 4, 3, 2, 1, 5, 4, 3, 2, 1, 5, 4, 3, 2, 1]);
     }
 
     #[test]
@@ -237,11 +254,4 @@ mod tests {
         let mut heap = from_vec::<int>(~[]);
         heap.replace(5);
     }
-
-    #[test]
-    fn test_to_vec() {
-        let data = ~[1, 3, 5, 7, 9, 2, 4, 6, 8, 0];
-        let heap = from_vec(copy data);
-        assert merge_sort(heap.to_vec(), le) == merge_sort(data, le);
-    }
 }

From 407b413f5319e34dd54bd4f88c6b9adc64ddc432 Mon Sep 17 00:00:00 2001
From: Daniel Micay <danielmicay@gmail.com>
Date: Tue, 11 Dec 2012 12:19:20 -0500
Subject: [PATCH 06/11] priority_queue: avoid copy with top and maybe_top

---
 src/libstd/priority_queue.rs | 23 ++++++++++++-----------
 1 file changed, 12 insertions(+), 11 deletions(-)

diff --git a/src/libstd/priority_queue.rs b/src/libstd/priority_queue.rs
index 35d238b4d7cc1..d73722dc55b9b 100644
--- a/src/libstd/priority_queue.rs
+++ b/src/libstd/priority_queue.rs
@@ -8,10 +8,10 @@ pub struct PriorityQueue <T: Copy Ord>{
 
 impl <T: Copy Ord> PriorityQueue<T> {
     /// Returns the greatest item in the queue - fails if empty
-    pure fn top(&self) -> T { self.data[0] }
+    pure fn top(&self) -> &self/T { &self.data[0] }
 
     /// Returns the greatest item in the queue - None if empty
-    pure fn maybe_top(&self) -> Option<T> {
+    pure fn maybe_top(&self) -> Option<&self/T> {
         if self.is_empty() { None } else { Some(self.top()) }
     }
 
@@ -151,7 +151,7 @@ mod tests {
         let mut sorted = merge_sort(data, le);
         let mut heap = from_vec(data);
         while heap.is_not_empty() {
-            assert heap.top() == sorted.last();
+            assert *heap.top() == sorted.last();
             assert heap.pop() == sorted.pop();
         }
     }
@@ -160,22 +160,22 @@ mod tests {
     fn test_push() {
         let mut heap = from_vec(~[2, 4, 9]);
         assert heap.len() == 3;
-        assert heap.top() == 9;
+        assert *heap.top() == 9;
         heap.push(11);
         assert heap.len() == 4;
-        assert heap.top() == 11;
+        assert *heap.top() == 11;
         heap.push(5);
         assert heap.len() == 5;
-        assert heap.top() == 11;
+        assert *heap.top() == 11;
         heap.push(27);
         assert heap.len() == 6;
-        assert heap.top() == 27;
+        assert *heap.top() == 27;
         heap.push(3);
         assert heap.len() == 7;
-        assert heap.top() == 27;
+        assert *heap.top() == 27;
         heap.push(103);
         assert heap.len() == 8;
-        assert heap.top() == 103;
+        assert *heap.top() == 103;
     }
 
     #[test]
@@ -241,11 +241,12 @@ mod tests {
 
     #[test]
     #[should_fail]
-    fn test_empty_top() { from_vec::<int>(~[]).top(); }
+    fn test_empty_top() { let empty = from_vec::<int>(~[]); empty.top(); }
 
     #[test]
     fn test_empty_maybe_top() {
-        assert from_vec::<int>(~[]).maybe_top().is_none();
+        let empty = from_vec::<int>(~[]);
+        assert empty.maybe_top().is_none();
     }
 
     #[test]

From b5aaa3c6f80cc1545a624e795f46c251cf865c14 Mon Sep 17 00:00:00 2001
From: Daniel Micay <danielmicay@gmail.com>
Date: Tue, 11 Dec 2012 17:34:50 -0500
Subject: [PATCH 07/11] priority_queue: fix siftup/siftdown naming

---
 src/libstd/priority_queue.rs | 22 +++++++++++-----------
 1 file changed, 11 insertions(+), 11 deletions(-)

diff --git a/src/libstd/priority_queue.rs b/src/libstd/priority_queue.rs
index d73722dc55b9b..fba9a8577a870 100644
--- a/src/libstd/priority_queue.rs
+++ b/src/libstd/priority_queue.rs
@@ -39,7 +39,7 @@ impl <T: Copy Ord> PriorityQueue<T> {
     /// Pop the greatest item from the queue - fails if empty
     fn pop(&mut self) -> T {
         let mut item = self.data.pop();
-        if self.is_not_empty() { item <-> self.data[0]; self.siftup(0); }
+        if self.is_not_empty() { item <-> self.data[0]; self.siftdown(0); }
         item
     }
 
@@ -51,7 +51,7 @@ impl <T: Copy Ord> PriorityQueue<T> {
     /// Push an item onto the queue
     fn push(&mut self, item: T) {
         self.data.push(item);
-        self.siftdown(0, self.len() - 1);
+        self.siftup(0, self.len() - 1);
     }
 
     /// Optimized version of a push followed by a pop
@@ -59,7 +59,7 @@ impl <T: Copy Ord> PriorityQueue<T> {
         let mut item = item;
         if self.is_not_empty() && self.data[0] > item {
             item <-> self.data[0];
-            self.siftup(0);
+            self.siftdown(0);
         }
         item
     }
@@ -68,7 +68,7 @@ impl <T: Copy Ord> PriorityQueue<T> {
     fn replace(&mut self, item: T) -> T {
         let mut item = item;
         item <-> self.data[0];
-        self.siftup(0);
+        self.siftdown(0);
         item
     }
 
@@ -82,7 +82,7 @@ impl <T: Copy Ord> PriorityQueue<T> {
         while end > 1 {
             end -= 1;
             q.data[end] <-> q.data[0];
-            unsafe { q.siftup_range(0, end) } // purity-checking workaround
+            unsafe { q.siftdown_range(0, end) } // purity-checking workaround
         }
         q.to_vec()
     }
@@ -92,12 +92,12 @@ impl <T: Copy Ord> PriorityQueue<T> {
         let mut n = q.len() / 2;
         while n > 0 {
             n -= 1;
-            unsafe { q.siftup(n) }; // purity-checking workaround
+            unsafe { q.siftdown(n) }; // purity-checking workaround
         }
         q
     }
 
-    priv fn siftdown(&mut self, startpos: uint, pos: uint) {
+    priv fn siftup(&mut self, startpos: uint, pos: uint) {
         let mut pos = pos;
         let newitem = self.data[pos];
 
@@ -114,7 +114,7 @@ impl <T: Copy Ord> PriorityQueue<T> {
         self.data[pos] = newitem;
     }
 
-    priv fn siftup_range(&mut self, pos: uint, endpos: uint) {
+    priv fn siftdown_range(&mut self, pos: uint, endpos: uint) {
         let mut pos = pos;
         let startpos = pos;
         let newitem = self.data[pos];
@@ -131,11 +131,11 @@ impl <T: Copy Ord> PriorityQueue<T> {
             childpos = 2 * pos + 1;
         }
         self.data[pos] = newitem;
-        self.siftdown(startpos, pos);
+        self.siftup(startpos, pos);
     }
 
-    priv fn siftup(&mut self, pos: uint) {
-        self.siftup_range(pos, self.len());
+    priv fn siftdown(&mut self, pos: uint) {
+        self.siftdown_range(pos, self.len());
     }
 }
 

From ccdfeca1e0775218625a382f17075b5768a10e3c Mon Sep 17 00:00:00 2001
From: Daniel Micay <danielmicay@gmail.com>
Date: Sat, 15 Dec 2012 11:15:25 -0500
Subject: [PATCH 08/11] priority_queue: fix test compilation

---
 src/libstd/priority_queue.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/libstd/priority_queue.rs b/src/libstd/priority_queue.rs
index fba9a8577a870..13cc5d854762a 100644
--- a/src/libstd/priority_queue.rs
+++ b/src/libstd/priority_queue.rs
@@ -143,7 +143,7 @@ impl <T: Copy Ord> PriorityQueue<T> {
 mod tests {
     use sort::merge_sort;
     use core::cmp::le;
-    use PriorityQueue::from_vec;
+    use priority_queue::PriorityQueue::from_vec;
 
     #[test]
     fn test_top_and_pop() {

From 78c8d31f1657a4f60525b2418941798bbe55306f Mon Sep 17 00:00:00 2001
From: Daniel Micay <danielmicay@gmail.com>
Date: Sat, 15 Dec 2012 12:14:07 -0500
Subject: [PATCH 09/11] priority_queue: clean up naming

---
 src/libstd/priority_queue.rs | 48 +++++++++++++++++-------------------
 1 file changed, 23 insertions(+), 25 deletions(-)

diff --git a/src/libstd/priority_queue.rs b/src/libstd/priority_queue.rs
index 13cc5d854762a..4f29c1ea97034 100644
--- a/src/libstd/priority_queue.rs
+++ b/src/libstd/priority_queue.rs
@@ -97,41 +97,39 @@ impl <T: Copy Ord> PriorityQueue<T> {
         q
     }
 
-    priv fn siftup(&mut self, startpos: uint, pos: uint) {
+    priv fn siftup(&mut self, start: uint, pos: uint) {
         let mut pos = pos;
-        let newitem = self.data[pos];
-
-        while pos > startpos {
-            let parentpos = (pos - 1) >> 1;
-            let parent = self.data[parentpos];
-            if newitem > parent {
-                self.data[pos] = parent;
-                pos = parentpos;
+        let new = self.data[pos];
+
+        while pos > start {
+            let parent = (pos - 1) >> 1;
+            if new > self.data[parent] {
+                self.data[pos] = self.data[parent];
+                pos = parent;
                 loop
             }
             break
         }
-        self.data[pos] = newitem;
+        self.data[pos] = new;
     }
 
-    priv fn siftdown_range(&mut self, pos: uint, endpos: uint) {
+    priv fn siftdown_range(&mut self, pos: uint, end: uint) {
         let mut pos = pos;
-        let startpos = pos;
-        let newitem = self.data[pos];
-
-        let mut childpos = 2 * pos + 1;
-        while childpos < endpos {
-            let rightpos = childpos + 1;
-            if rightpos < endpos &&
-                   !(self.data[childpos] > self.data[rightpos]) {
-                childpos = rightpos;
+        let start = pos;
+        let new = self.data[pos];
+
+        let mut child = 2 * pos + 1;
+        while child < end {
+            let right = child + 1;
+            if right < end && !(self.data[child] > self.data[right]) {
+                child = right;
             }
-            self.data[pos] = self.data[childpos];
-            pos = childpos;
-            childpos = 2 * pos + 1;
+            self.data[pos] = self.data[child];
+            pos = child;
+            child = 2 * pos + 1;
         }
-        self.data[pos] = newitem;
-        self.siftup(startpos, pos);
+        self.data[pos] = new;
+        self.siftup(start, pos);
     }
 
     priv fn siftdown(&mut self, pos: uint) {

From 07d91b2cb05fdad425b770776ec4bc8bf6c59911 Mon Sep 17 00:00:00 2001
From: Daniel Micay <danielmicay@gmail.com>
Date: Sat, 15 Dec 2012 13:24:10 -0500
Subject: [PATCH 10/11] priority_queue: replace copies with moves

---
 src/libstd/priority_queue.rs | 34 ++++++++++++++++++++++++----------
 1 file changed, 24 insertions(+), 10 deletions(-)

diff --git a/src/libstd/priority_queue.rs b/src/libstd/priority_queue.rs
index 4f29c1ea97034..c62b3897c30af 100644
--- a/src/libstd/priority_queue.rs
+++ b/src/libstd/priority_queue.rs
@@ -1,12 +1,18 @@
 
 /// A priority queue implemented with a binary heap
 use core::cmp::Ord;
+use ptr::addr_of;
 
-pub struct PriorityQueue <T: Copy Ord>{
+#[abi = "rust-intrinsic"]
+extern "C" mod rusti {
+    fn move_val_init<T>(dst: &mut T, -src: T);
+}
+
+pub struct PriorityQueue <T: Ord>{
     priv data: ~[T],
 }
 
-impl <T: Copy Ord> PriorityQueue<T> {
+impl <T: Ord> PriorityQueue<T> {
     /// Returns the greatest item in the queue - fails if empty
     pure fn top(&self) -> &self/T { &self.data[0] }
 
@@ -97,26 +103,33 @@ impl <T: Copy Ord> PriorityQueue<T> {
         q
     }
 
-    priv fn siftup(&mut self, start: uint, pos: uint) {
+    // The implementations of siftup and siftdown use unsafe blocks in order to
+    // move an element out of the vector (leaving behind a junk element), shift
+    // along the others and move it back into the vector over the junk element.
+    // This reduces the constant factor compared to using swaps, which involves
+    // twice as many moves.
+
+    priv fn siftup(&mut self, start: uint, pos: uint) unsafe {
         let mut pos = pos;
-        let new = self.data[pos];
+        let new = move *addr_of(&self.data[pos]);
 
         while pos > start {
             let parent = (pos - 1) >> 1;
             if new > self.data[parent] {
-                self.data[pos] = self.data[parent];
+                rusti::move_val_init(&mut self.data[pos],
+                                     move *addr_of(&self.data[parent]));
                 pos = parent;
                 loop
             }
             break
         }
-        self.data[pos] = new;
+        rusti::move_val_init(&mut self.data[pos], move new);
     }
 
-    priv fn siftdown_range(&mut self, pos: uint, end: uint) {
+    priv fn siftdown_range(&mut self, pos: uint, end: uint) unsafe {
         let mut pos = pos;
         let start = pos;
-        let new = self.data[pos];
+        let new = move *addr_of(&self.data[pos]);
 
         let mut child = 2 * pos + 1;
         while child < end {
@@ -124,11 +137,12 @@ impl <T: Copy Ord> PriorityQueue<T> {
             if right < end && !(self.data[child] > self.data[right]) {
                 child = right;
             }
-            self.data[pos] = self.data[child];
+            rusti::move_val_init(&mut self.data[pos],
+                                 move *addr_of(&self.data[child]));
             pos = child;
             child = 2 * pos + 1;
         }
-        self.data[pos] = new;
+        rusti::move_val_init(&mut self.data[pos], move new);
         self.siftup(start, pos);
     }
 

From d25b0aac50133e848547c7653ae6798b10e5f550 Mon Sep 17 00:00:00 2001
From: Daniel Micay <danielmicay@gmail.com>
Date: Sat, 15 Dec 2012 14:29:38 -0500
Subject: [PATCH 11/11] priority_queue: add docstring for from_vec

---
 src/libstd/priority_queue.rs | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/libstd/priority_queue.rs b/src/libstd/priority_queue.rs
index c62b3897c30af..bb9d5f5261f64 100644
--- a/src/libstd/priority_queue.rs
+++ b/src/libstd/priority_queue.rs
@@ -93,6 +93,7 @@ impl <T: Ord> PriorityQueue<T> {
         q.to_vec()
     }
 
+    /// Create a PriorityQueue from a vector (heapify)
     static pub pure fn from_vec(xs: ~[T]) -> PriorityQueue<T> {
         let mut q = PriorityQueue{data: xs,};
         let mut n = q.len() / 2;