Implement equality operators

Make SortedArray appear Equatable by implementing == and != for
SortedArrays where the elements are Equatable.

Author: klaaspieter

Sources/SortedArray.swift

@@ -313,3 +313,11 @@ extension SortedArray {
         return .notFound(insertAt: left)
     }
 }
+
+public func ==<Element: Equatable> (lhs: SortedArray<Element>, rhs: SortedArray<Element>) -> Bool {
+  return lhs._elements == rhs._elements
+}
+
+public func !=<Element: Equatable> (lhs: SortedArray<Element>, rhs: SortedArray<Element>) -> Bool {
+  return lhs._elements != rhs._elements
+}

Tests/SortedArrayTests/SortedArrayTests.swift

@@ -219,6 +219,18 @@ class SortedArrayTests: XCTestCase {
         sut.remove(3)
         assertElementsEqual(sut, [1,2])
     }
+
+  func testIsEqual() {
+    let sut = SortedArray(unsorted: 1...3)
+
+    XCTAssertTrue(sut == SortedArray(unsorted: 1...3))
+  }
+
+  func testIsNotEqual() {
+    let sut = SortedArray(unsorted: 1...3)
+
+    XCTAssertTrue(sut != SortedArray(unsorted: 1...4))
+  }
 }
 
 extension SortedArrayTests {
@@ -258,6 +270,8 @@ extension SortedArrayTests {
             ("testRemoveElementAtBeginningPreservesSortOrder", testRemoveElementAtBeginningPreservesSortOrder),
             ("testRemoveElementInMiddlePreservesSortOrder", testRemoveElementInMiddlePreservesSortOrder),
             ("testRemoveElementAtEndPreservesSortOrder", testRemoveElementAtEndPreservesSortOrder),
+            ("testImplements==", testIsEqual),
+            ("testImplements!=", testIsNotEqual),
         ]
     }
 }