Master Go Arrays: Definitions, Initialization, and Traversal Explained

Preface

Hey everyone, I'm 星期八 and we continue learning Go arrays.

What is an array

My summary: an array is a variable that points to a contiguous block of memory with a fixed length and elements of the same type.

How to define an array

var variableName [size]elementType

Example:

package main

func main() {
    // Declare a name_list array of length 100 that holds strings
    var name_list [100]string
}

Note:

var variableName [size]elementType is equivalent to var variableName variableType
So var name1 [3]int != var name2 [4]int because their types differ and cannot be assigned directly.

Array initialization

package main

import "fmt"

func main() {
    // Method 1: declare without assigning
    // var name_list [10]int
    // fmt.Println(name_list) // [0 0 0 0 0 0 0 0 0 0]
    // Method 2: partially assign
    // var name_list [10]int = [10]int{1, 3}
    // fmt.Println(name_list) // [1 3 0 0 0 0 0 0 0 0]
    // Method 3: full assignment with type inference
    // var name_list = [3]int{1, 6, 10}
    // fmt.Println(name_list) // [1 6 10]
    // Method 4: let compiler infer length
    // var name_list = [...]int{1, 2, 4, 5, 19}
    // fmt.Println(name_list) // [1 2 4 5 19]
    // Method 5: indexed assignment (rare)
    var name_list = [...]int{1: 66, 4: 11} // index 1 = 66, index 4 = 11
    fmt.Println(name_list) // [0 66 0 0 11]
}

Array traversal

package main

import "fmt"

func main() {
    var name_list = [...]string{"张三", "李四", "王五", "小刘"}
    // Method 1: classic for loop (commented)
    // for i := 0; i < len(name_list); i++ {
    //     fmt.Println(name_list[i])
    // }
    // Method 2: for range
    for index, name := range name_list {
        fmt.Println(index, name)
    }
}

Multidimensional arrays

Two‑dimensional arrays

Usually a two‑dimensional array is sufficient; three dimensions are the practical limit.

Define a two‑dimensional array

package main

import "fmt"

func main() {
    // Define a 3x2 array
    var student_list = [3][2]string{{"张三", "李四"}, {"王五", "小刘"}, {"小七", "王八"}}
    fmt.Println(student_list)
}

Iterate a two‑dimensional array

Two nested loops are needed.

package main

import "fmt"

func main() {
    var student_list = [3][2]string{{"张三", "李四"}, {"王五", "小刘"}, {"小七", "王八"}}
    // Method 1: classic for loops (commented)
    // for i := 0; i < len(student_list); i++ {
    //     for j := 0; j < len(student_list[i]); j++ {
    //         fmt.Println(student_list[i][j])
    //     }
    // }
    // Method 2: for range
    for _, row := range student_list {
        for _, col := range row {
            fmt.Println(col)
        }
    }
}

Can length be inferred for multidimensional arrays?

Attempting to use [...] for both dimensions causes a compilation error:

Using inference only on the first dimension works:

package main

import "fmt"

func main() {
    var student_list = [...][2]string{{"张三", "李四"}, {"王五", "小刘"}, {"小七", "王八"}}
    fmt.Println(student_list)
}

Note: Length inference is allowed for the first dimension.

Summary

We have covered Go arrays, including their definition, declaration, initialization, traversal, and usage of multidimensional arrays.

If you have questions, leave a comment; the author will respond promptly.