Added product function to Sequence (#1168)

CHANGELOG.md

@@ -10,6 +10,9 @@ The changelog for **SwifterSwift**. Also see the [releases](https://github.com/S
 ### Added
 - **Measurement**
   - Added `+=`, `-=`, `*=`, `/=` to add, subtract, multiply and divide measurements. [#1162](https://github.com/SwifterSwift/SwifterSwift/pull/1162) by [Roman Podymov](https://github.com/RomanPodymov)
+- **Sequence**
+  - Added `product()` for calculating the product of all `Numeric` elements. [#1168](https://github.com/SwifterSwift/SwifterSwift/pull/1168) by [MartonioJunior](https://github.com/MartonioJunior)
+  - Added `product(for:)` for calculating the product of the `Numeric` property for all elements in `Sequence`. [#1168](https://github.com/SwifterSwift/SwifterSwift/pull/1168) by [MartonioJunior](https://github.com/MartonioJunior)
 - **UIView**
   - Added `removeBlur()` method for removing the applied blur effect from the view. [#1159](https://github.com/SwifterSwift/SwifterSwift/pull/1159) by [regi93](https://github.com/regi93)
   - Added `makeCircle(diameter:)` method to make the view circular. [#1165](https://github.com/SwifterSwift/SwifterSwift/pull/1165) by [happyduck-git](https://github.com/happyduck-git)

Sources/SwifterSwift/SwiftStdlib/SequenceExtensions.swift

@@ -225,6 +225,16 @@ public extension Sequence {
         // Inspired by: https://swiftbysundell.com/articles/reducers-in-swift/
         return reduce(.zero) { $0 + $1[keyPath: keyPath] }
     }
+
+    /// SwifterSwift: Product of all elements in sequence.
+    ///
+    ///        ["James", "Wade", "Bryant"].product(for: \.count) -> 120
+    ///
+    /// - Parameter map: Mapping function to `Numeric` value.
+    /// - Returns: product of the sequence's elements.
+    func product<T: Numeric>(for map: (Element) -> T) -> T {
+        reduce(1) { $0 * map($1) }
+    }
 
     /// SwifterSwift: Returns the first element of the sequence with having property by given key path equals to given
     /// `value`.
@@ -308,3 +318,14 @@ public extension Sequence where Element: AdditiveArithmetic {
         return reduce(.zero, +)
     }
 }
+
+// MARK: - Methods (Numeric)
+
+public extension Sequence where Element: Numeric {
+    /// SwifterSwift: Product of all elements in sequence.
+    ///
+    ///        [1, 2, 3, 4, 5].product() -> 120
+    ///
+    /// - Returns: product of the sequence's elements.
+    func product() -> Element { reduce(1, *) }
+}

Tests/SwiftStdlibTests/SequenceExtensionsTests.swift

@@ -134,6 +134,16 @@ final class SequenceExtensionsTests: XCTestCase {
         XCTAssertEqual(["James", "Wade", "Bryant"].sum(for: \.count), 15)
         XCTAssertEqual(["a", "b", "c", "d"].sum(for: \.count), 4)
     }
+
+    func testProduct() {
+        XCTAssertEqual([1, 2, 3, 4, 5].product(), 120)
+        XCTAssertEqual([1.2, 2.3, 3.4, 4.5, 5.6].product(), 236.4768, accuracy: 0.001)
+    }
+
+    func testMapFunctionProduct() {
+        XCTAssertEqual(["James", "Wade", "Bryant"].product(for: \.count), 120)
+        XCTAssertEqual(["a", "b", "c", "d"].product(for: \.count), 1)
+    }
 
     func testKeyPathSorted() {
         let array = ["James", "Wade", "Bryant"]