1 位運算符
- 按位取反運算符
let initialBits: UInt8 = 0b00001111
let invertedBits = ~initialBits // 等于 0b11110000
- 按位與運算符
let firstSixBits: UInt8 = 0b11111100
let lastSixBits: UInt8 = 0b00111111
let middleFourBits = firstSixBits & lastSixBits // 等于 00111100
- 按位或運算符
let someBits: UInt8 = 0b10110010
let moreBits: UInt8 = 0b01011110
let combinedbits = someBits | moreBits // 等于 11111110
- 按位異或運算符
let firstBits: UInt8 = 0b00010100
let otherBits: UInt8 = 0b00000101
let outputBits = firstBits ^ otherBits // 等于 00010001
- 按位左移、右移運算符
let shiftBits: UInt8 = 4 // 00000100
shiftBits << 1 // 00001000
shiftBits << 2 // 00010000
shiftBits << 5 // 10000000
shiftBits << 6 // 00000000
shiftBits >> 2 // 00000001
- 使用移位運算對顏色進行RGB分解
let pink: UInt32 = 0xCC6699
let redComponent = (pink & 0xFF0000) >> 16 // redComponent 是 0xCC，即 204
let greenComponent = (pink & 0x00FF00) >> 8 // greenComponent 是 0x66， 即 102
let blueComponent = pink & 0x0000FF // blueComponent 是 0x99，即 153
- 有符號整數的移位運算
2 溢出運算符
在默認情況下，當向一個整數賦予超過它容量的值時，Swift默認會報錯，而不是生成一個無效的數。
var potentialOverflow = Int16.max // potentialOverflow 的值是 32767，這是 Int16 能容納的最大整數
//potentialOverflow += 1 // 這里會報錯
// 可以選擇讓系統在數值溢出的時候采取截斷處理，而非報錯。 `&+` `&-` `&*`
var unsignedOverflow = UInt8.max // unsignedOverflow 等于 UInt8 所能容納的最大整數 255
unsignedOverflow = unsignedOverflow &+ 1 // 此時 unsignedOverflow 等于 0
var unsignedOverflow2 = UInt8.min // unsignedOverflow 等于 UInt8 所能容納的最小整數 0
unsignedOverflow2 = unsignedOverflow2 &- 1 // 此時 unsignedOverflow 等于 255
3 優先級和結合性
4 運算符函數
運算符重載: 類和結構體可以為現有的運算符提供自定義的實現。
例子：向量的相加
struct Vector2D {
var x = 0.0, y = 0.0
}
extension Vector2D {
static func + (left: Vector2D, right: Vector2D) -> Vector2D {
return Vector2D(x: left.x + right.x, y: left.y + right.y)
}
static prefix func - (vector: Vector2D) -> Vector2D {
return Vector2D(x: -vector.x, y: -vector.y)
}
static func += (left: inout Vector2D, right: Vector2D) {
left = left + right
}
static func == (left: Vector2D, right: Vector2D) -> Bool {
return (left.x == right.x) && (left.y == right.y)
}
static func != (left: Vector2D, right: Vector2D) -> Bool {
return !(left == right)
}
}
let vector = Vector2D(x: 3.0, y: 1.0)
let anotherVector = Vector2D(x: 2.0, y: 4.0)
let combinedVector = vector + anotherVector // combinedVector 是一個新的 Vector2D 實例，值為 (5.0, 5.0)
let negative = -vector // negative 是一個值為 (-3.0, -1.0) 的 Vector2D 實例
var original = Vector2D(x: 1.0, y: 2.0)
let vectorToAdd = Vector2D(x: 3.0, y: 4.0)
original += vectorToAdd // original 的值現在為 (4.0, 6.0)
let twoThree = Vector2D(x: 2.0, y: 3.0)
let anotherTwoThree = Vector2D(x: 2.0, y: 3.0)
if twoThree == anotherTwoThree {
print("These two vectors are equivalent.")
}
5 自定義運算符
prefix operator +++
extension Vector2D {
static prefix func +++ (vector: inout Vector2D) -> Vector2D {
vector += vector
return vector
}
}
var toBeDoubled = Vector2D(x: 1.0, y: 4.0)
let afterDoubling = +++toBeDoubled
// toBeDoubled now has values of (2.0, 8.0)
// afterDoubling also has values of (2.0, 8.0)
infix operator +-: AdditionPrecedence
extension Vector2D {
static func +- (left: Vector2D, right: Vector2D) -> Vector2D {
return Vector2D(x: left.x + right.x, y: left.y - right.y)
}
}
let firstVector = Vector2D(x: 1.0, y: 2.0)
let secondVector = Vector2D(x: 3.0, y: 4.0)
let plusMinusVector = firstVector +- secondVector
// plusMinusVector is a Vector2D instance with values of (4.0, -2.0)
playground文件在andyRon/LearnSwift
