Added support for == operator and initialization from pairs

Sources/OrderedDictionary.swift

@@ -8,7 +8,7 @@
 
 /// The `OrderedDictionary` is a collection which combines the features of `Dictionary` and `Array`.
 /// It maps keys to values and additionally sorts the key-value pairs by zero-based integer index.
-public struct OrderedDictionary<Key : Hashable, Value>: CollectionType, ArrayLiteralConvertible, CustomStringConvertible {
+public struct OrderedDictionary<Key: Hashable, Value>: CollectionType, ArrayLiteralConvertible, CustomStringConvertible {
 
     // MARK: - Initialization
 
@@ -17,14 +17,18 @@ public struct OrderedDictionary<Key : Hashable, Value>: CollectionType, ArrayLit
         self.keysToValues = [:]
     }
 
-    public init(arrayLiteral elements: Element...) {
+    public init(elements: [Element]) {
         self.init()
 
         for element in elements {
             self[element.0] = element.1
         }
     }
 
+    public init(arrayLiteral elements: Element...) {
+        self.init(elements: elements)
+    }
+
     // MARK: - Type Aliases
 
     public typealias Element = (Key, Value)
@@ -168,3 +172,7 @@ public struct OrderedDictionary<Key : Hashable, Value>: CollectionType, ArrayLit
     public var endIndex: Index { return orderedKeys.endIndex }
 
 }
+
+public func == <Key: Equatable, Value: Equatable>(lhs: OrderedDictionary<Key, Value>, rhs: OrderedDictionary<Key, Value>) -> Bool {
+    return lhs.orderedKeys == rhs.orderedKeys && lhs.keysToValues == rhs.keysToValues
+}

Tests/OrderedDictionaryTests.swift

@@ -40,6 +40,16 @@ class OrderedDictionaryTests: XCTestCase {
         expect(self.orderedDictionary.containsKey("C")) == true
     }
 
+    func testInitializationUsingPairs() {
+        let elements = [
+            ("A", 1),
+            ("B", 2),
+            ("C", 3)
+        ]
+
+        expect(OrderedDictionary(elements: elements) == self.orderedDictionary).to(beTrue())
+    }
+
     func testElementsGenerator() {
         for entry in self.orderedDictionary.enumerate() {
             expect(self.orderedDictionary[entry.index].0) == entry.element.0