{ (x1, x2) in x1 + x2 } // as is { let (x1, x2) = $0; x1 + x2 } // to be なのは流石に笑うObservable.zip(e0, e1).map { (a0: Int, a1: Int) -> Int in a0 + a1 } // ↓ Observable.zip(e0, e1).map { (__val:(Int, Int)) -> Int in let (a0,a1) = __val; a0 + a1 } これどうなんだw