Range Keyword in Golang

28 Jun, 2021
In Golang Range keyword is used in different kinds of data structures in order to iterates over elements. The range keyword is mainly used in for loops in order to iterate over all the elements of a map, slice, channel, or an array. When it iterates over the elements of an array and slices then it returns the index of the element in an integer form. And when it iterates over the elements of a map then it returns the key of the subsequent key-value pair. Moreover, range can either returns one value or two values. Lets see what range returns while iterating over different kind of collections in Golang.
Array or slice: The first value returned in case of array or slice is index and the second value is element.
String: The first value returned in string is index and the second value is rune int.
Map: The first value returned in map is key and the second value is the value of the key-value pair in map.
Channel: The first value returned in channel is element and the second value is none.
Now, let’s see some examples to illustrate the usage of range keyword in Golang.
Example 1:
// Golang Program to illustrate the usage// of range keyword over items of an// array in Golang package main import "fmt" // main functionfunc main() {     // Array of odd numbers    odd := [7]int{1, 3, 5, 7, 9, 11, 13}     // using range keyword with for loop to    // iterate over the array elements    for i, item := range odd {         // Prints index and the elements        fmt.Printf("odd[%d] = %d \n", i, item)    }}
Output:
odd[0] = 1
odd[1] = 3
odd[2] = 5
odd[3] = 7
odd[4] = 9
odd[5] = 11
odd[6] = 13

Here, all the elements are printed with their respective index.
Example 2:
// Golang Program to illustrate the usage of// range keyword over string in Golang package main import "fmt" // Constructing main functionfunc main() {     // taking a string    var string = "GeeksforGeeks"     // using range keyword with for loop to    // iterate over the string    for i, item := range string {         // Prints index of all the        // characters in the string        fmt.Printf("string[%d] = %d \n", i, item)    }}
Output:
string[0] = 71 
string[1] = 101 
string[2] = 101 
string[3] = 107 
string[4] = 115 
string[5] = 102 
string[6] = 111 
string[7] = 114 
string[8] = 71 
string[9] = 101 
string[10] = 101 
string[11] = 107 
string[12] = 115

Here, the items printed is the rune, that is int32 ASCII value of the stated characters that forms string.
Example 3:
// Golang Program to illustrate the usage of// range keyword over maps in Golang package main import "fmt" // main functionfunc main() {     // Creating map of student ranks    student_rank_map := map[string]int{"Nidhi": 3,                           "Nisha": 2, "Rohit": 1}     // Printing map using keys only    for student := range student_rank_map {        fmt.Println("Rank of", student, "is: ",                     student_rank_map[student])    }     // Printing maps using key-value pair    for student, rank := range student_rank_map {        fmt.Println("Rank of", student, "is: ", rank)    }}
Output:
Rank of Nidhi is:  3
Rank of Nisha is:  2
Rank of Rohit is:  1
Rank of Nidhi is:  3
Rank of Nisha is:  2
Rank of Rohit is:  1

So, here at first the output is printed only using key then again output is printed using both key and value.
anikakapoor
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