Generic Operator

>>(_:_:)

Returns the result of shifting a value’s binary representation the specified number of digits to the right.

Declaration

static func >> <Other>(lhs: Int32, rhs: Other) -> Int32 where Other : BinaryInteger

Parameters

lhs

The value to shift.

rhs

The number of bits to shift lhs to the right.

Discussion

The >> operator performs a smart shift, which defines a result for a shift of any value.

  • Using a negative value for rhs performs a left shift using abs(rhs).

  • Using a value for rhs that is greater than or equal to the bit width of lhs is an overshift. An overshift results in -1 for a negative value of lhs or 0 for a nonnegative value.

  • Using any other value for rhs performs a right shift on lhs by that amount.

The following example defines x as an instance of UInt8, an 8-bit, unsigned integer type. If you use 2 as the right-hand-side value in an operation on x, the value is shifted right by two bits.

let x: UInt8 = 30                 // 0b00011110
let y = x >> 2
// y == 7                         // 0b00000111

If you use 11 as rhs, x is overshifted such that all of its bits are set to zero.

let z = x >> 11
// z == 0                         // 0b00000000

Using a negative value as rhs is the same as performing a left shift using abs(rhs).

let a = x >> -3
// a == 240                       // 0b11110000
let b = x << 3
// b == 240                       // 0b11110000

Right shift operations on negative values “fill in” the high bits with ones instead of zeros.

let q: Int8 = -30                 // 0b11100010
let r = q >> 2
// r == -8                        // 0b11111000

let s = q >> 11
// s == -1                        // 0b11111111