Array Subscript

Array+Subscript

• guard subscription returns nil when the index is out of bounds

let array = [1, 2, 3, 4, 5]

array[guard: 6] ?? 0 //0
array[guard: 1] ?? 0 //2

• reduct

[1, 2, 3, 4].reduct(+) // Optional(10)
[9, 3, 2, 1].reduct(-) // Optional(3)
[1, 2, 3, 4].reduct(*) // Optional(24)