What does a >> mean in Go language?

Question

I’m looking for information on Google’s Go language. In “A Tour of Go” they have this code:

const (
    Big = 1<<100
    Small = Big>>99
)

But what do << and >> mean?

You can see all of the code at http://tour.golang.org/#14

Answer 1

They are bitwise shift operators. x << y means x × 2^y, while x >> y means x × 2^−y or, equivalently, x ÷ 2^y. These operators are generally used to manipulate the binary representation of a value, where, just like with a power of 10 in decimal, multiplying or dividing by a power of two has the effect of “shifting” the digits left or right, respectively:

// Left shift:

  13 *  2 ==    26 // decimal
1101 * 10 == 11010 // binary (13 is 8 + 4 + 0 + 1)

// Right shift (brackets denote discarded portion):

  13 /  2 ==   6[.5] // decimal
1101 / 10 == 110[.1] // binary

Because you are operating on integers and a right shift typically results in fractional values, there are a couple of ways to handle how the result of a right shift is rounded. In Go, right shift is a logical shift on unsigned values and an arithmetic shift on signed values. Logical shift always rounds toward zero, while arithmetic shift always rounds down, that is, toward −∞.