Go by Example: Arrays

In Go, an array is a numbered sequence of elements of a specific length. In typical Go code, slices are much more common; arrays are useful in some special scenarios.

 
package main

import "fmt"

func main() {

Here we create an array a that will hold exactly 5 ints. The type of elements and length are both part of the array’s type. By default an array is zero-valued, which for ints means 0s.

 
    var a [5]int
    fmt.Println("emp:", a)

We can set a value at an index using the array[index] = value syntax, and get a value with array[index].

 
    a[4] = 100
    fmt.Println("set:", a)
    fmt.Println("get:", a[4])

The builtin len returns the length of an array.

 
    fmt.Println("len:", len(a))

Use this syntax to declare and initialize an array in one line.

 
    b := [5]int{1, 2, 3, 4, 5}
    fmt.Println("dcl:", b)

Array types are one-dimensional, but you can compose types to build multi-dimensional data structures.

 
    var twoD [2][3]int
    for i := 0; i < 2; i++ {
        for j := 0; j < 3; j++ {
            twoD[i][j] = i + j
        }
    }
    fmt.Println("2d: ", twoD)

2 arrays are comparable

 
    var arr [5]int
    arr[4] = 100
    arr2 := [5]int{0, 0, 0, 0, 100}
    fmt.Println("arr == arr2: ", arr == arr2)

copy array re-assign array will be directly copied, and original arr will not be affected

 
    arr = [5]int{0, 0, 0, 0, 100}
    arr3 := arr
    arr3[4] = 200
    fmt.Println("arr[4] = ", arr[4])

reverse array

 
    arr = [5]int{1, 2, 3, 4, 100}
    rev(&arr) // should pass array with refrence
    fmt.Println("reversed arr = ", arr)
}

func rev(arr *[5]int) {
    n := len(arr)
    for i := 0; i < n/2; i++ {
        arr[i], arr[n-1-i] = arr[n-1-i], arr[i]
    }
}

Note that arrays appear in the form [v1 v2 v3 ...] when printed with fmt.Println.

 
$ go run arrays.go
emp: [0 0 0 0 0]
set: [0 0 0 0 100]
get: 100
len: 5
dcl: [1 2 3 4 5]
2d:  [[0 1 2] [1 2 3]]
arr == arr2: true
arr[4] =  100
reversed arr = [100 4 3 2 1]

Next example: Slices.

source
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