I didn't know about "fold"... In Swift it's still call `reduce` even if your accumulator type is arbitrary: https://developer.apple.com/documentation/swift/arr

I didn't know about "fold"... In Swift it's still call `reduce` even if your accumulator type is arbitrary: https://developer.apple.com/documentation/swift/array/2298686-reduce https://developer.apple.com/documentation/swift/array/229868...