Learn Go - Constants Summary

constants.go

// Constants Examples
package main

import "fmt"

// enumerated constants
const (
	e1 = iota
	e2 // it is inferring iota
	e3 // it is inferring iota
)

const (
	e4 = iota // will always start at 0 as the block. Typically you want 'zero' to indicate a value not assigned
	e5        // if you are checking to see if something equials a particular constant
	e6
)

const (
	_  = iota // similar to the above, but throwing away the 0 value. you can also change
	e7        // where iota starts by adding to it i.e. iota+5
	e8
)

const (
	_  = iota // example of assigning constants to size values
	KB = 1 << (10 * iota)
	MB
	GB
	TB
	PB
	EB
	ZB
	YB
)

const (
	isAdmin          = 1 << iota // 00000001
	isHeadquarters               // 00000010
	canSeeFinancials             // 00000100
	canSeeAfrica                 // 00001000
	canSeeAsia
	canSeeEurope
	canSeeNorthAmerica
	canSeeSouthAmerica
)

func main() {
	const myConst int = 42 // still use camel case, this is a typed constant

	fmt.Printf("%v, %T\n", myConst, myConst)

	const a = 42     // compiler can infer, including when using in calculations because
	var b int16 = 27 // it is just replacing the name 'a' with the value 42 in this code essentially

	fmt.Printf("%v, %T\n", a, a)
	fmt.Printf("%v, %T\n", a+b, a+b)

	// enumerated constants
	fmt.Printf("%v, %T\n", e1, e1)
	fmt.Printf("%v, %T\n", e2, e2)
	fmt.Printf("%v, %T\n", e3, e3)
	fmt.Printf("%v, %T\n", e4, e4)
	fmt.Printf("%v, %T\n", e5, e5)
	fmt.Printf("%v, %T\n", e6, e6)
	fmt.Printf("%v, %T\n", e7, e7)
	fmt.Printf("%v, %T\n", e8, e8)

	var roles byte = isAdmin | canSeeFinancials | canSeeEurope
	fmt.Printf("%b\n", roles)
	fmt.Printf("Is Admin? %v\n", isAdmin&roles == isAdmin)
	fmt.Printf("Is Headquarters? %v\n", isHeadquarters&roles == isHeadquarters)
}