Merge pull request #37 from apple/sync

Add uniqueElements extension on Collection

Author: aciidgh

Sources/TSCBasic/CollectionExtensions.swift

@@ -23,3 +23,20 @@ extension Collection {
         }
     }
 }
+
+extension Collection where Element: Hashable {
+    /// Returns a new list of element removing duplicate elements.
+    ///
+    /// Note: The order of elements is preseved.
+    /// Complexity: O(n)
+    public func spm_uniqueElements() -> [Element] {
+        var set = Set<Element>()
+        var result = [Element]()
+        for element in self {
+            if set.insert(element).inserted {
+                result.append(element)
+            }
+        }
+        return result
+    }
+}

Tests/TSCBasicTests/CollectionExtensionsTests.swift

@@ -17,4 +17,10 @@ class CollectionExtensionsTests: XCTestCase {
         XCTAssertEqual([42].spm_only, 42)
         XCTAssertEqual([42, 24].spm_only, nil)
     }
+
+    func testUniqueElements() {
+        XCTAssertEqual([1, 2, 2, 4, 2, 1, 1, 4].spm_uniqueElements(), [1, 2, 4])
+        XCTAssertEqual([1, 2, 2, 4, 2, 1, 1, 4, 9].spm_uniqueElements(), [1, 2, 4, 9])
+        XCTAssertEqual([3, 2, 1].spm_uniqueElements(), [3, 2, 1])
+    }
 }

Tests/TSCBasicTests/XCTestManifests.swift

@@ -59,6 +59,7 @@ extension CollectionExtensionsTests {
     // to regenerate.
     static let __allTests__CollectionExtensionsTests = [
         ("testOnly", testOnly),
+        ("testUniqueElements", testUniqueElements),
     ]
 }