‏prefix و suffix و dropFirst

prefix(n)

let arr = [1, 2, 3, 4, 5]
print(Array(arr.prefix(3)))
print(Array(arr.prefix(99)))

suffix(n)

let arr = [1, 2, 3, 4, 5]
print(Array(arr.suffix(2)))
print(Array(arr.suffix(0)))

dropFirst

let arr = [10, 20, 30, 40]
print(Array(arr.dropFirst()))
print(Array(arr.dropFirst(2)))

dropLast

let arr = [10, 20, 30, 40]
print(Array(arr.dropLast()))
print(Array(arr.dropLast(3)))

كلها تعيد شرائح

let arr = [1, 2, 3, 4]
let s = arr.prefix(2)
print(type(of: s))

آمنة مع قيم n الكبيرة

let arr = [1, 2]
print(Array(arr.prefix(10)))
print(Array(arr.dropFirst(10)))

prefix(while:)

let arr = [2, 4, 6, 7, 8]
let evensAtStart = arr.prefix(while: { $0 % 2 == 0 })
print(Array(evensAtStart))

drop(while:)

let arr = [2, 4, 6, 7, 8]
let rest = arr.drop(while: { $0 % 2 == 0 })
print(Array(rest))

دمج الدوال

let arr = [10, 20, 30, 40, 50]
let middle = arr.dropFirst().dropLast()
print(Array(middle))

نمط المعاينة مقابل الإزالة

let queue = [100, 200, 300]
if let head = queue.first {
    let tail = Array(queue.dropFirst())
    print("head:", head, "tail:", tail)
}

وضوح المقصود

let arr = [1, 2, 3, 4, 5, 6]
print(Array(arr.suffix(3)))

اختبار سريع

مراجعة

let arr = [1, 2, 3, 4, 5]
print(Array(arr.prefix(2)), Array(arr.suffix(2)), Array(arr.dropFirst()))