Mastering the for Loop in Go: The Only Loop You Need

In Go, the for loop is the only looping construct you need. Unlike many other programming languages that have multiple types of loops (such as while and do-while), Go simplifies things by using the versatile for loop to handle all iterative tasks. By understanding the different ways to use for loops, you can solve a wide range of programming problems efficiently.

In this article, we will cover:

1. Basic for loop

2. Condition-based for loop (similar to while loop)

3. Infinite for loop

4. Using for loop with range

5. Nested for loops

6. Breaking out of a loop and using continue

Let’s explore each concept with examples and detailed explanations.

---

1. Basic for Loop

The most common form of the for loop includes an initialization, a condition, and a post-statement.

Syntax

for initialization; condition; post {
    // Code to execute in each iteration
}

Example 1: Basic for Loop

package main

import "fmt"

func main() {
    for i := 0; i < 5; i++ {
        fmt.Println("Iteration:", i)
    }
}

Code Explanation

• Line 5: The for loop starts with the initialization i := 0, sets the condition i < 5, and increments i with i++ in each iteration.

• Line 6: Inside the loop, we print the value of i for each iteration.

• Line 7: The loop ends when i is no longer less than 5.

Output

Iteration: 0
Iteration: 1
Iteration: 2
Iteration: 3
Iteration: 4

Key Points:

• The loop starts with i = 0 and continues until i reaches 5.

• The value of i is incremented by 1 after each iteration (i++ is shorthand for i = i + 1).

---

2. Condition-based for Loop (Similar to while Loop)

You can use the for loop in Go as a while loop by omitting the initialization and post-statement.

Example 2: Condition-based for Loop

package main

import "fmt"

func main() {
    count := 1

    for count <= 5 {
        fmt.Println("Count:", count)
        count++
    }
}

Code Explanation

• Line 5: We initialize the variable count to 1.

• Line 7: The for loop checks the condition count <= 5 before each iteration.

• Line 8: Inside the loop, we print the value of count.

• Line 9: We increment count by 1 in each iteration.

• Line 10: The loop ends when count becomes greater than 5.

Output

Count: 1
Count: 2
Count: 3
Count: 4
Count: 5

Key Points:

• This form of the for loop behaves like a while loop in other languages.

• It keeps iterating as long as the condition is true.

---

3. Infinite for Loop

An infinite loop is a loop that runs forever until it is explicitly stopped using a break statement.

Example 3: Infinite for Loop

package main

import "fmt"

func main() {
    i := 0

    for {
        fmt.Println("Infinite loop iteration:", i)
        i++
        if i >= 3 {
            break
        }
    }
}

Code Explanation

• Line 5: We initialize the variable i to 0.

• Line 7: The for loop has no condition, making it an infinite loop.

• Line 9: We increment i and check if it is greater than or equal to 3.

• Line 10: The break statement exits the loop when i is 3.

Output

Infinite loop iteration: 0
Infinite loop iteration: 1
Infinite loop iteration: 2

Key Points:

• Infinite loops can be useful in certain situations, such as server applications that need to run continuously.

• Always include a break statement or a condition to exit the loop to prevent it from running indefinitely.

---

4. Using for Loop with range

The range keyword is used to iterate over elements of arrays, slices, maps, or strings.

Example 4: Iterating Over an Array with range

package main

import "fmt"

func main() {
    numbers := []int{10, 20, 30, 40, 50}

    for index, value := range numbers {
        fmt.Println("Index:", index, "Value:", value)
    }
}

Code Explanation

• Line 5: We define an array numbers with 5 integers.

• Line 7: The for loop uses range to iterate over numbers.

• Line 8: index is the index of the current element, and value is its value.

• Line 9: We print both the index and value in each iteration.

Output

Index: 0 Value: 10
Index: 1 Value: 20
Index: 2 Value: 30
Index: 3 Value: 40
Index: 4 Value: 50

Key Points:

• The range keyword simplifies looping through collections like arrays and slices.

• You can use _ as a placeholder if you don’t need the index or value.

---

5. Nested for Loops

You can use a for loop inside another for loop to iterate through multidimensional data structures.

Example 5: Nested for Loop

package main

import "fmt"

func main() {
    for i := 1; i <= 3; i++ {
        for j := 1; j <= 3; j++ {
            fmt.Println("i:", i, "j:", j)
        }
    }
}

Code Explanation

• Line 5: The outer loop iterates with i from 1 to 3.

• Line 6: The inner loop iterates with j from 1 to 3 for each value of i.

• Line 7: We print the values of i and j in each iteration.

Output

i: 1 j: 1
i: 1 j: 2
i: 1 j: 3
i: 2 j: 1
i: 2 j: 2
i: 2 j: 3
i: 3 j: 1
i: 3 j: 2
i: 3 j: 3

Key Points:

• Nested loops are useful for working with multidimensional data structures like matrices.

• Be careful with nested loops as they can become computationally expensive.

---

6. Breaking Out of a Loop and Using continue

You can use the break statement to exit a loop early and the continue statement to skip to the next iteration.

Example 6: Using break and continue

package main

import "fmt"

func main() {
    for i := 1; i <= 10; i++ {
        if i%2 == 0 {
            continue
        }
        if i > 7 {
            break
        }
        fmt.Println("Odd number:", i)
    }
}

Code Explanation

• Line 5: The loop iterates from 1 to 10.

• Line 6: If i is even (i%2 == 0), the continue statement skips the rest of the loop body.

• Line 8: If i is greater than 7, the break statement exits the loop.

• Line 10: We print the value of i if it is odd and less than or equal to 7.

Output

Odd number: 1
Odd number: 3
Odd number: 5
Odd number: 7

---

Conclusion

In this article, we covered:

• The basic for loop and its components.

• Using the for loop as a condition-based loop (like a while loop).

• Infinite loops and how to break out of them.

• Iterating through collections using range.

• Nested loops for handling complex data structures.

• Using break and continue for controlling loop flow.

The for loop in Go is versatile and powerful, making it the only loop you need to master. In upcoming articles, we’ll dive deeper into functions, error handling, and more advanced Go programming concepts.

Happy coding with Go, and stay tuned for more tutorials!