Rewrite BinaryInteger+Addition.swift tests (#108) (#110).

Sources/TestKit2/Utilities+Reduce.swift

@@ -0,0 +1,36 @@
+//=----------------------------------------------------------------------------=
+// This source file is part of the Ultimathnum open source project.
+//
+// Copyright (c)  2023 Oscar Byström Ericsson
+// Licensed under Apache License, Version 2.0
+//
+// See http://www.apache.org/licenses/LICENSE-2.0 for license information.
+//=----------------------------------------------------------------------------=
+
+//*============================================================================*
+// MARK: * Utilities x Reduce
+//*============================================================================*
+
+@inlinable public func reduce<T>(
+    _ transform: (consuming T) throws -> T,
+    _ rhs: T
+)   rethrows -> T {
+    try transform(rhs)
+}
+
+@inlinable public func reduce<T>(
+    _ lhs: consuming T,
+    _ transform: (consuming T, borrowing T) throws -> T,
+    _ rhs: borrowing T
+)   rethrows -> T {
+    try transform(lhs, rhs)
+}
+
+@inlinable public func reduce<T>(
+    _ lhs: consuming T,
+    _ transform: (inout T, borrowing T) throws -> Void,
+    _ rhs: borrowing T
+)   rethrows -> T {
+    try transform(&lhs, rhs)
+    return lhs
+}