Constants and iota enums

Context

iota is a predeclared identifier in Go that represents successive untyped integer constants. It is used to create enumerated constants (enums) easily.

• iota resets to 0 at the start of each const block.
• Within the block, each const line increments iota by 1.

Example

Define days of the week and bit flags using iota.

Code example

package main

import "fmt"

const (
    Sunday = iota  // 0
    Monday         // 1
    Tuesday        // 2
    Wednesday      // 3
    Thursday       // 4
    Friday         // 5
    Saturday       // 6
)

const (
    Read = 1 << iota  // 1 << 0 = 1
    Write             // 1 << 1 = 2
    Exec              // 1 << 2 = 4
)

func main() {
    fmt.Println(Sunday, Monday, Tuesday)
    fmt.Println(Read, Write, Exec)
}

Output

0 1 2
1 2 4

Useful links

• Go specification: Iota
• Go by Example: Constants and iota