Arrays

An array holds a fixed number of values of one type. The length is part of the type: [3]int and [4]int are different, incompatible types.

Syntax

var scores [3]int                  // [0 0 0] — zero values
primes := [5]int{2, 3, 5, 7, 11}   // array literal
days := [...]string{"Mon", "Tue"}  // length counted for you: [2]string

Example

package main

import "fmt"

func main() {
    var scores [3]int
    scores[0] = 90
    scores[2] = 75
    fmt.Println(scores, len(scores))

    primes := [5]int{2, 3, 5, 7, 11}
    copied := primes // copies all five values
    copied[0] = 100
    fmt.Println(primes[0], copied[0])

    total := 0
    for _, p := range primes {
        total += p
    }
    fmt.Println("sum:", total)
}

Expected output

[90 0 75] 3
2 100
sum: 28

Arrays are values: assigning one to another variable, or passing it to a function, copies every element. That's the key difference from slices, which you'll meet next.

In practice, arrays are used less often than slices — mainly when the size is truly fixed (like the 3 bytes of an RGB color). Most Go code reaches for slices instead.

Common mistakes

• Reading or writing past the end. With a constant index this is a compile error (invalid argument: index 3 out of bounds [0:3]); with a variable index the program panics at runtime.
• Expecting an array to grow — it can't. Use a slice when the size changes.

Practice

Create an array of 4 temperatures, then use a loop to find and print the highest one.

package main

import "fmt"

func main() {
    temps := [4]int{21, 27, 19, 24}

    highest := temps[0]
    for _, t := range temps {
        if t > highest {
            highest = t
        }
    }
    fmt.Println(highest) // 27
}