Swift演算子まとめ ref: https://qiita.com/KentaKudo/items/a1dd2eb0bf37302c1c81

file0.swift

let result = 2 + 3 + 4  // 左から

var str1: String?
var str2: String?
let string = str1 ?? str2 ?? "string" // 右から

let int1 = 1
let int2 = 2
let int3 = 3
int1 == int2 == int3 // エラー

file1.swift

let (x, y) = (1, 2)
// x = 1, y = 2

if x = y { // 判定する値が返らない
    // エラー
}

file10.swift

0...100 ~= 15 // true

file11.swift

0...100 ~= 100 // true

file12.swift

0..<100 ~= 100 // false

file13.swift

var isSelected: Bool = true
!isSelected // false

file14.swift

let bit: UInt8 = 0b00001111 // = 15
// ↓
~bit // 0b11110000 = 240

file15.swift

let bit1: UInt8 = 0b11111100 // = 252
let bit2: UInt8 = 0b11110000 // = 240
// ↓
bit1 & bit2 // 0b11110000 = 240

file16.swift

let bit1: UInt8 = 0b11111100 // = 252
let bit2: UInt8 = 0b11110000 // = 240
// ↓
bit1 | bit2 // 0b11111100 = 252

file17.swift

let bit1: UInt8 = 0b11111100 // = 252
let bit2: UInt8 = 0b11110000 // = 240
// ↓
bit1 ^ bit2 // 0b00001100 = 12

file18.swift

let unsignedInt: UInt8 = 0b11111111 // 255
// ↓
unsignedInt << 4 // 0b11110000 = 240
unsignedInt >> 4 // 0b00001111 = 15

file19.swift

let signedPlusInt: Int8 = 127 // 0b0_1111111
signedPlusInt >> 4 // 0b0_0000111 = 7
signedPlusInt << 4 // 0b1_1110000 = -16
// 空いた桁を0で埋めている

let signedMinusInt: Int8 = -127 // 0b1_0000000
signedMinusInt >> 4 // 0b1_1111000 = -8
signedMinusInt << 4 // 0b0_0001111 = 16
// 空いた桁を1で埋めている

file2.swift

var i: Int8 = 127 // Int8の最大数
i++  // エラー

file20.swift

var int: Int = 3

int += 5
// ↓同じ
int = int + 5


var bit: UInt8 = 0b11110000 // 240

bit <<= 4 // 0b00000000 = 0
// ↓同じ
bit = bit << 4

file21.swift

let str: Any = "string"
str is String // true

file22.swift

let str: String = "string"
str as NSString

file23.swift

let str: Any = "string"
str as! Int // 実行時エラー
str as? Int // nil

file24.swift

// * を + に書き換え
func * (left: Int, right: Int) -> Int {
    return left + right
}

2 * 3 // 5

// 左側；String、右側：Intに + を定義
func + (left: String, right: Int) -> String {
    return left + String(right)
}

"Number: " + 3 // "Number: 3"

file25.swift

// 累乗を計算する演算子を定義
infix operator ** { associativity left precedence 161 }
func ** (left: Int, right: UInt) -> Int {
    var powered = 1
    for _ in 0..<right {
        powered *= left
    }

    return powered
}

2 + 3 ** 2 // 11

file3.txt

a = (b * 整数) + 余り

file4.swift

-9 % 4 // (4 * -2) - 1 
// -1
-9 % -4 // (-4 * 2) - 1 
// -1

file5.swift

8 % 2.5 // 0.5

file6.swift

var a = 0, b = 0
let c = ++a // 1
let d = b++ // 0

file7.swift

var i: Int8 = 127 // Int8の最大数
i &+ 1 // -128: Int8の最小数

file8.swift

let isSelected = true

if isSelected {
    print("true")
} else {
    print("false")
}
// ↓同じ
isSelected ? print("true") : print("false")

file9.swift

let alpha: Int? = nil
let beta: Int = 10

alpha != nil ? alpha! : beta
// ↓同じ
alpha ?? beta