Loops in Golang

• on 4 Aug 2023
• By psid
• Golang

Loops in Golang

In Go, loops are used to repeat a block of code multiple times until a certain condition is met. Go supports three types of loops: for loop, while loop (implemented using for loop), and do-while loop (implemented using for loop with a break statement).

1. For Loop:
   • The for loop in Go is the most commonly used loop and follows a similar structure to other programming languages.
   • It has three components: initialization, condition, and increment/decrement.
   • The loop will continue as long as the condition is true.

Syntax:

for initialization; condition; increment/decrement {
    // Code to be repeated
}

Example :

package main

import "fmt"

func main() {
    for i := 1; i <= 5; i++ {
        fmt.Println("Iteration:", i)
    }
}

Output :

Iteration: 1
Iteration: 2
Iteration: 3
Iteration: 4
Iteration: 5

2. While Loop (Implemented using For Loop):
   • Go does not have a specific while loop, but you can create a while loop behavior using the for loop with only a condition.
   • The loop will run as long as the condition is true.

Syntax:

for condition {
    // Code to be repeated
}

Example :

package main

import "fmt"

func main() {
    i := 1
    for i <= 5 {
        fmt.Println("Iteration:", i)
        i++
    }
}

Output :

Iteration: 1
Iteration: 2
Iteration: 3
Iteration: 4
Iteration: 5

3. Do-While Loop (Implemented using For Loop with Break):
   • Go does not have a direct do-while loop, but you can achieve its behavior using a for loop with a break statement.
   • The loop will run at least once, and then it will continue as long as the condition is true.

Syntax:

for {
    // Code to be repeated
    if condition {
        break
    }
}

Example :

package main

import "fmt"

func main() {
    i := 1
    for {
        fmt.Println("Iteration:", i)
        i++
        if i > 5 {
            break
        }
    }
}

Output :

Iteration: 1
Iteration: 2
Iteration: 3
Iteration: 4
Iteration: 5

These loop constructs in Go allow you to efficiently execute repetitive tasks and control the flow of your program based on specific conditions. You can choose the appropriate loop type depending on the nature of your task and the desired behavior of the loop.

Range in Loops

In Go, the range keyword is used in a for loop to iterate over elements in various data structures such as arrays, slices, strings, maps, and channels. It simplifies the process of iterating over the elements of a collection without needing to use traditional indexing or explicit iteration variables.

The syntax for using range in a for loop is as follows:

for index, value := range collection {
    // Code to be executed for each element (value) in the collection
}

Here’s how range works with different data structures:

1. Arrays and Slices:
   • When used with arrays or slices, range returns the index and value of each element in the collection.

Example:

package main

import "fmt"

func main() {
    numbers := []int{1, 2, 3, 4, 5}

    for index, value := range numbers {
        fmt.Printf("Index: %d, Value: %d\n", index, value)
    }
}

Output :

Index: 0, Value: 1
Index: 1, Value: 2
Index: 2, Value: 3
Index: 3, Value: 4
Index: 4, Value: 5

2. Strings:
   • When used with a string, range iterates over each Unicode code point (character) in the string.

Example:

package main

import "fmt"

func main() {
    message := "Hello, Go!"

    for index, char := range message {
        fmt.Printf("Index: %d, Character: %c\n", index, char)
    }
}

Output :

Index: 0, Character: H
Index: 1, Character: e
Index: 2, Character: l
Index: 3, Character: l
Index: 4, Character: o
Index: 5, Character: ,
Index: 6, Character:  
Index: 7, Character: G
Index: 8, Character: o
Index: 9, Character: !

3. Maps:
   • When used with maps, range iterates over key-value pairs, providing both the key and the corresponding value.

Example:

package main

import "fmt"

func main() {
    ages := map[string]int{
        "John": 30,
        "Jane": 25,
        "Tom": 35,
    }

    for name, age := range ages {
        fmt.Printf("%s is %d years old\n", name, age)
    }
}

Output :

John is 30 years old
Jane is 25 years old
Tom is 35 years old

Using range in for loops is a concise and idiomatic way to iterate over elements in collections, making your code more readable and maintainable. It simplifies the process of accessing elements and their corresponding indices or keys, providing an elegant solution for handling data structures.