Chapter 3 of 20

Operators

Arithmetic / comparison / logic / bitwise / assignment

Arithmetic Operators

+ - * / : the usual four operations
% : remainder (integers only)
++ / -- : increment/decrement — statements only, not expressions

package main

import "fmt"

func main() {
    a, b := 7, 3
    fmt.Println(a/b) // 2  (integer division)
    fmt.Println(a%b) // 1
    a++              // valid
    fmt.Println(a)
    // fmt.Println(a++) // compile error: a++ is not an expression
}

Comparison and Logic

== != < <= > >= return a bool; the logical operators && || ! use short-circuit evaluation.

package main

import "fmt"

func main() {
    age, name := 20, "Alice"
    ok := age >= 18 && name != ""
    if !ok {
        fmt.Println("invalid")
        return
    }
    fmt.Println("ok:", name)
}

Bitwise Operations

& bitwise AND, | bitwise OR, ^ XOR
&^ bit clear (AND NOT)
<< left shift, >> right shift

package main

import "fmt"

func main() {
    flags := 0b1010
    fmt.Printf("%04b\n", flags|0b0101)  // 1111
    fmt.Printf("%04b\n", flags&^0b0010) // 1000
    fmt.Printf("%04b\n", flags<<1)      // 10100
}

Compound Assignment

package main

import "fmt"

func main() {
    x := 10
    x += 5  // 15
    x *= 2  // 30
    x >>= 1 // 15
    fmt.Println(x)
}

Operator Precedence

Go's precedence is simpler than C's: unary > multiplication-division/bitwise > addition-subtraction/bitwise > comparison > && > ||. Use parentheses liberally so readers don't have to consult a table.