Arrays

As always, arrays start a position zero. They are also fixed in size, the length cannot be modified once an array is declared. For more flexibility see slices in the next section.

Initialize array

Define an array declaring the number of elements and the data element, for example:

var myArray [5]int

If you print this out as-is, Go will initialize each element to zero:

main.go

package main

import "fmt"

func main() {
    var myArray [5]int
    fmt.Println(myArray)
}

go run .

[0 0 0 0 0]

Populating array

You can define the initial values using the following syntax, remember we can omit the var syntax and use colon/equals :=:

main.go

package main

import "fmt"

func main() {
    myArray := [5]int{1976, 2024, 1992, 1986, 2004}
    fmt.Println(myArray)
}

Accessing array

You can access a specific element within an array, for example to print the first element:

main.go

package main

import "fmt"

func main() {
    myArray := [5]int{1976, 2024, 1992, 1986, 2004}
    fmt.Println(myArray[0])
}

Modify array

Likewise, you can modify the value of an element:

main.go

package main

import "fmt"

func main() {
    myArray := [5]int{1976, 2024, 1992, 1986, 2004}
    fmt.Println(myArray[1])
    myArray[1] = 1066
    fmt.Println(myArray[1])
}

Length of array

To determine the length of an array:

main.go

package main

import "fmt"

func main() {
    myArray := [5]int{1976, 2024, 1992, 1986, 2004}
    fmt.Println(len(myArray))
}

Copy Array

Understand the behavior when making copies of arrays.

main.go

package main

import "fmt"

func main() {
    myArray := [5]string{"dog", "cat", "rabbit", "duck", "mouse"}
    fmt.Println(myArray)

    animals := myArray
    fmt.Println(animals)
}

If you make changes to either myArray or animals there are now independent arrays, one dose not effect the other.

main.go

package main

import "fmt"

func main() {
    myArray := [5]string{"dog", "cat", "rabbit", "duck", "mouse"}

    animals := myArray

    myArray[0] = "lizard"
    animals[0] = "snail"

    fmt.Println(myArray)
    fmt.Println(animals)
}

Output:

[lizard cat rabbit duck mouse]
[snail cat rabbit duck mouse]

Compare

You can compare all data types in Go. When comparing arrays, the data type must match, for example you can't compare an array of integers against and array of strings or else you'll get a compile error.

The following example with print out true then false:

main.go

package main

import "fmt"

func main() {
    myArray := [5]string{"dog", "cat", "rabbit", "duck", "mouse"}
    animals := myArray

    myBool := myArray == animals
    fmt.Println(myBool)

    animals[0] = "snail"

    myBool = myArray == animals
    fmt.Println(myBool)
}