const and iota

Learn const for constants and iota for auto-increment.

Constant values use the const keyword. After const Pi = 3.14, Pi cannot be changed; it is a compile error.

For enum-like structures, Go uses iota. In a const block, iota increments on each line; the first line starts at 0.

Constants are computed at compile time and do not change at runtime. This makes them preferred for performance and safety.

Using iota

iota produces a line-by-line incrementing number in a const block. For example:

const ( A = iota B C )

Here A=0, B=1, C=2. This is the standard way to define enum-like constants.

iota also works with bitwise ops: 1 << iota yields powers of two on each line.

Define the constants Pazartesi (0), Sali and Carsamba with iota in a const block. Print fmt.Println(Pazartesi, Sali, Carsamba).

Show example solution

package main

import "fmt"

const (
    Pazartesi = iota
    Sali
    Carsamba
)

func main() {
    fmt.Println(Pazartesi, Sali, Carsamba)
}

Constant declaration

To declare the constant Pi:
____ Pi = 3.14

Show answer

To declare the constant Pi:
const Pi = 3.14

Next lesson: Zero value