Added .reduce which assumes reducing into 0 when elements are additive

README.md

@@ -82,3 +82,28 @@ print( 0.clamping(within: 2...7)) // Prints 2
 print( 5.clamping(within: 2...7)) // Prints 5
 print(99.clamping(within: 2...7)) // Prints 7
 ```
+
+
+
+# Additive Reduction #
+
+This introduces a `.reduce(_:)` function to sequences whose elements conform to `AdditiveArithmetic` which assumes you're reducing into `.zero`:
+
+```swift
+// Before
+bunchaNumbers.reduce(into: 0) { $0 = max($0, $1) }
+
+// After
+bunchaNumbers.reduce { $0 = max($0, $1) }
+```
+
+
+This also adds a convenience function `.sum()`, build on this new reducer:
+
+```swift
+// Before
+bunchaNumbers.reduce(into: 0, +=)
+
+// After
+bunchaNumbers.sum()
+```

Sources/BasicMathTools/additive reductions.swift

@@ -0,0 +1,31 @@
+//
+//  additive reductions.swift
+//
+//
+//  Created by The Northstar✨ System on 2023-11-30.
+//
+
+import Foundation
+
+
+
+public extension Sequence where Element: AdditiveArithmetic {
+
+    /// Reduces this collection to a single value, assuming the result should be of the same type as each element, and that the starting value for reduction is `.zero`
+    ///
+    /// - Parameters:
+    ///   - reducer: Processes each element and reduces this collection to a single value
+    ///    - result: The running result of reduction (starts with `.zero`)
+    ///    - each: Each element of the sequence
+    ///
+    /// - Returns: The whole collection, reduced down to a single value
+    func reduce(_ reducer: (_ result: inout Element, _ each: Element) -> Void) -> Element {
+        reduce(into: .zero, reducer)
+    }
+
+
+    /// Returns the sum of all elements in this sequence
+    func sum() -> Element {
+        reduce(+=)
+    }
+}

Tests/BasicMathToolsTests/additive reductions tests.swift

@@ -0,0 +1,31 @@
+//
+//  additive reductions tests.swift
+//  
+//
+//  Created by The Northstar✨ System on 2023-11-30.
+//
+
+import XCTest
+import BasicMathTools
+
+
+
+final class additive_reductions_tests: XCTestCase {
+    func testSum() {
+        XCTAssertEqual(29, [1, 2, 3, 5, 7, 11].sum())
+        XCTAssertEqual(0, [1, -1, 1, -1, 1, -1].sum())
+    }
+
+
+    func testReduce() {
+        XCTAssertEqual(-58, [1, 2, 3, 5, 7, 11].reduce { result, each in
+            result = (result - (each * 2))
+        })
+
+        XCTAssertEqual(-29, [1, 2, 3, 5, 7, 11].reduce(-=))
+
+        XCTAssertEqual(0, [1, 2, 3, 5, 7, 11].reduce(*=))
+
+        XCTAssertEqual(56, [8, -31, 11, -13, 56, 27, -2].reduce { $0 = max($0, $1) })
+    }
+}