Constants #

Go supports constants of character, string, boolean, and numeric values.

const declares a constant value.

package main

import "fmt"

const s string = "constant"

func main() {
	fmt.Println(s)
	// Output: constant
}

A const statement can appear anywhere a var statement can.

package main

func main() {
	const n = 500000000
	fmt.Println(n)
	// Output: 500000000
}

Constant expressions perform arithmetic with arbitrary precision.

const n = 500000000
const d = 3e20 / n
fmt.Println(d)
// Output: 6e+11

A numeric constant has no type until it’s given one, such as by an explicit conversion.

const d = 6e+11
fmt.Println(int64(d))
// Output: 600000000000

A number can be given a type by using it in a context that requires one, such as a variable assignment or function call. For example, here math.Sin expects a float64.

const n = 500000000
fmt.Println(math.Sin(n))
// Output: -0.28470407323754404