diff --git a/PriorityQueue/PriorityQueue.swift b/PriorityQueue/PriorityQueue.swift
index df5be22..708738d 100644
--- a/PriorityQueue/PriorityQueue.swift
+++ b/PriorityQueue/PriorityQueue.swift
@@ -9,20 +9,20 @@
 import Foundation
 
 public class PriorityQueue<T> {
-
+    
     private final var _heap: [T]
     private let compare: (T, T) -> Bool
-
-    public init(_ compare: (T, T) -> Bool) {
+    
+    public init(_ compare: @escaping (T, T) -> Bool) {
         _heap = []
         self.compare = compare
     }
-
+    
     public func push(newElement: T) {
         _heap.append(newElement)
-        siftUp(_heap.endIndex - 1)
+        siftUp(index: _heap.endIndex - 1)
     }
-
+    
     public func pop() -> T? {
         if _heap.count == 0 {
             return nil
@@ -30,17 +30,17 @@ public class PriorityQueue<T> {
         if _heap.count == 1 {
             return _heap.removeLast()
         }
-        swap(&_heap[0], &_heap[_heap.endIndex - 1])
+        _heap.swapAt(0, _heap.endIndex - 1)
         let pop = _heap.removeLast()
-        siftDown(0)
+        siftDown(index: 0)
         return pop
     }
-
+    
     private func siftDown(index: Int) -> Bool {
         let left = index * 2 + 1
         let right = index * 2 + 2
         var smallest = index
-
+        
         if left < _heap.count && compare(_heap[left], _heap[smallest]) {
             smallest = left
         }
@@ -48,21 +48,21 @@ public class PriorityQueue<T> {
             smallest = right
         }
         if smallest != index {
-            swap(&_heap[index], &_heap[smallest])
-            siftDown(smallest)
+            _heap.swapAt(index, smallest)
+            siftDown(index: smallest)
             return true
         }
         return false
     }
-
+    
     private func siftUp(index: Int) -> Bool {
         if index == 0 {
             return false
         }
         let parent = (index - 1) >> 1
         if compare(_heap[index], _heap[parent]) {
-            swap(&_heap[index], &_heap[parent])
-            siftUp(parent)
+            _heap.swapAt(index, parent)
+            siftUp(index: parent)
             return true
         }
         return false
@@ -73,54 +73,54 @@ extension PriorityQueue {
     public var count: Int {
         return _heap.count
     }
-
+    
     public var isEmpty: Bool {
         return _heap.isEmpty
     }
-
-    public func update<T2 where T2: Equatable>(element: T2) -> T? {
+    
+    public func update<T2>(element: T2) -> T? where T2: Equatable {
         assert(element is T)  // How to enforce this with type constraints?
-        for (index, item) in _heap.enumerate() {
+        for (index, item) in _heap.enumerated() {
             if (item as! T2) == element {
                 _heap[index] = element as! T
-                if siftDown(index) || siftUp(index) {
+                if siftDown(index: index) || siftUp(index: index) {
                     return item
                 }
             }
         }
         return nil
     }
-
-    public func remove<T2 where T2: Equatable>(element: T2) -> T? {
+    
+    public func remove<T2>(element: T2) -> T? where T2: Equatable {
         assert(element is T)  // How to enforce this with type constraints?
-        for (index, item) in _heap.enumerate() {
+        for (index, item) in _heap.enumerated() {
             if (item as! T2) == element {
-                swap(&_heap[index], &_heap[_heap.endIndex - 1])
+                _heap.swapAt(index, _heap.endIndex - 1)
                 _heap.removeLast()
-                siftDown(index)
+                siftDown(index: index)
                 return item
             }
         }
         return nil
     }
-
+    
     public var heap: [T] {
         return _heap
     }
-
+    
     public func removeAll() {
         _heap.removeAll()
     }
 }
 
-extension PriorityQueue: GeneratorType {
+extension PriorityQueue: IteratorProtocol {
     public typealias Element = T
     public func next() -> Element? {
         return pop()
     }
 }
 
-extension PriorityQueue: SequenceType {
+extension PriorityQueue: Sequence {
     public typealias Generator = PriorityQueue
     public func generate() -> Generator {
         return self