按位运算符

~

1变0，0变1。

let initialBits: UInt8 = 0b00001111
let invertedBits = ~initialBits  // equals 11110000

$

全1得1，其他为0

let firstSixBits: UInt8 = 0b11111100
let lastSixBits: UInt8  = 0b00111111
let middleFourBits = firstSixBits & lastSixBits  // equals 00111100

|

有1得1，其他为0

let someBits: UInt8 = 0b10110010
let moreBits: UInt8 = 0b01011110
let combinedbits = someBits | moreBits  // equals 11111110

^

相异为1，相同为0

let firstBits: UInt8 = 0b00010100
let otherBits: UInt8 = 0b00000101
let outputBits = firstBits ^ otherBits  // equals 00010001

<<和>>

<<整体左移，右边填0；

>> 整体右移，左边填0。

let shiftBits: UInt8 = 4   // 00000100 in binary
shiftBits << 1             // 00001000
shiftBits << 2             // 00010000
shiftBits << 5             // 10000000
shiftBits << 6             // 00000000
shiftBits >> 2             // 00000001

算子函数

上面讲解的都是简单的运算符，下面的是为对象添加运算符，使之可计算。

符号在中间

struct Vector2D {
    var x = 0.0,y = 0.0
}

func + (left: Vector2D,right: Vector2D) -> Vector2D {
    return Vector2D(x: left.x + right.x,y: left.y + right.y)
}

let vector = Vector2D(x: 3.0,y: 1.0)
let anotherVector = Vector2D(x: 2.0,y: 4.0)
let combinedVector = vector + anotherVector
// combinedVector is a Vector2D instance with values of (5.0,5.0)

前缀和后缀

前缀关键字prefix
后缀关键字postfix

prefix func - (vector: Vector2D) -> Vector2D {
    return Vector2D(x: -vector.x,y: -vector.y)
}

let positive = Vector2D(x: 3.0,y: 4.0)
let negative = -positive
// negative is a Vector2D instance with values of (-3.0,-4.0)
let alsoPositive = -negative
// alsoPositive is a Vector2D instance with values of (3.0,4.0)

复合赋值运算符

这里用+=举例。

func += (inout left: Vector2D,right: Vector2D) {
    left = left + right
}

var original = Vector2D(x: 1.0,y: 2.0)
let vectorToAdd = Vector2D(x: 3.0,y: 4.0)
original += vectorToAdd
// original now has values of (4.0,6.0)

其他

参考资料

The Swift Programming Language (Swift 2.1)

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