Stores the result of shifting a value’s binary representation the specified number of digits to the left in the left-hand-side variable.

static func <<= <Other>(lhs: inout Self, rhs: Other) where Other : BinaryInteger



The value to shift.


The number of bits to shift lhs to the left.


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

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

  • Using a value for rhs that is greater than or equal to the bit width of lhs is an overshift, resulting in zero.

  • Using any other value for rhs performs a left 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 left by two bits.

var x: UInt8 = 30                 // 0b00011110
x <<= 2
// x == 120                       // 0b01111000

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

var y: UInt8 = 30                 // 0b00011110
y <<= 11
// y == 0                         // 0b00000000

Using a negative value as rhs is the same as performing a right shift with abs(rhs).

var a: UInt8 = 30                 // 0b00011110
a <<= -3
// a == 3                         // 0b00000011

var b: UInt8 = 30                 // 0b00011110
b >>= 3
// b == 3                         // 0b00000011