There is only one looping construct in Golang, and that is the for loop. The for loop in Golang has three components, which must be separated by semicolons (;), those are:
- The initialization statement: which is executed before the first iteration. e.g. i := 0
- The condition expression: which is executed just before every iteration. e.g. i < 5
- The Post statement: which is executed at the end of every iteration. e.g. i++
There is no need for any parentheses for enclosing those three components, but to define a block we must use braces { }.
for i := 0 ; i < 5 ; i++{
// statements to execute......
}
The initialization and post statements are optional.
i:=0
for ; i < 5;{
i++
}
You can use for loop as while loop in Golang. Just drop all the semicolons.
i := 0
for i < 5 {
i++
}
Infnite Loop: If there is no condition statement, the loop becomes an infinite loop.
for {
}
Example:
package main import "fmt" // function to print numbers 0 // to 9 and print the sum of 0 to 9 func main() { // variable to store the sum sum := 0 // this is a for loop which runs from 0 to 9 for i := 0; i < 10; i++ { // printing the value of // i : the iterating variable fmt.Printf("%d ", i) // calculating the sum sum += i } fmt.Printf("\nsum = %d", sum) } |
Output:
0 1 2 3 4 5 6 7 8 9 sum = 45
In Golang there is no foreach loop instead, the for loop can be used as “foreach“. There is a keyword range, you can combine for and range together and have the choices of using the key or value within the loop.
Syntax:
for <key>, <value> := range <container>{
}
Here,
- key and value: It can be any variable you want to choose.
- container: It can be any variable which is an array, list, map, etc.
Example 1:
package main import "fmt" // Driver function to show the // use of for and range together func main() { // here we used a map of integer to string mapp := map[int]string{1: "one", 2: "two", 3: "three"} // integ act as keys of mapp // spell act as the values of // mapp which is mapped to integ for integ, spell := range mapp { // using integ and spell as // key and value of the map fmt.Println(integ, " = ", spell) } } |
Output:
1 = one 2 = two 3 = three
Example 2:
package main import "fmt" // Driver function to show the // use of for and range together func main() { // declaring an array of integers arra := []int{1, 2, 3, 4} // traversing through the array for index, itr := range arra { // the key or value variables // used in for syntax // depends on the container. // If its an array or list, // the key refers to the index... fmt.Print(index, " : ", itr, "\n") } // if we use only one // variable in the for loop, // it by default refers to // the value in the container. for itr := range arra { fmt.Print(it, " ") } } |
Output:
0 : 1 1 : 2 2 : 3 3 : 4 1 2 3 4
