**Course Title:** Mastering Go: From Basics to Advanced Development **Section Title:** Control Structures and Functions **Topic:** Loops: for, range. Loops are a fundamental control structure in programming that enable repetitive execution of a block of code for a specified number of iterations. In this topic, we'll explore the `for` and `range` loops in Go, discussing their syntax, usage, and practical examples. ### For Loop The `for` loop is a general-purpose loop that allows you to iterate over a sequence of values. The basic syntax is as follows: ```go for initialization; condition; post { // code to execute } ``` Here: * `initialization` is an optional statement that sets up the loop variable. * `condition` is a boolean expression that determines whether the loop should continue. * `post` is an optional statement that's executed after each iteration. Let's consider a simple example to illustrate the use of a `for` loop: ```go package main import "fmt" func main() { for i := 0; i < 5; i++ { fmt.Println(i) } } ``` In this example, we declare a loop variable `i` with an initial value of 0. The condition `i < 5` ensures that the loop runs five times. After each iteration, `i` is incremented by 1. ### Range Loop The `range` loop is specifically designed for iterating over arrays, slices, strings, maps, and channels. The basic syntax is as follows: ```go for key, value := range myArray { // code to execute } ``` Here: * `key` represents the index or key of the current element. * `value` represents the value of the current element. Let's consider an example to illustrate the use of a `range` loop with an array: ```go package main import "fmt" func main() { colors := [3]string{"Red", "Green", "Blue"} for i, color := range colors { fmt.Printf("Index %d: Color = %s\n", i, color) } } ``` In this example, we use the `range` loop to iterate over the `colors` array. For each iteration, we get the index `i` and the corresponding `color`. ### Range Loop with Slices When using `range` with slices, it's essential to note that the index is still valid, even if the slice is resized. However, if you want to modify the slice while iterating, use the `for i := range mySlice` syntax to avoid issues. Let's consider an example to illustrate this: ```go package main import "fmt" func main() { numbers := []int{1, 2, 3, 4, 5} for i, num := range numbers { if i == 2 { numbers = append(numbers, 6) } fmt.Println(num) } fmt.Println("Updated slice:", numbers) } ``` In this example, we append a new element to the `numbers` slice during the iteration. If we used the `range` loop without keeping track of the index `i`, we might miss the newly appended element. ### Range Loop with Maps When using `range` with maps, we don't get an index. Instead, we get the key and the corresponding value. The order of iteration over a map is unpredictable, and we might not get the items in the same order as they were inserted. Let's consider an example to illustrate the use of a `range` loop with a map: ```go package main import "fmt" func main() { person := map[string]string{ "name": "John", "age": "30", "city": "New York", } for key, value := range person { fmt.Printf("Key: %s, Value: %s\n", key, value) } } ``` In this example, we use the `range` loop to iterate over the `person` map. For each iteration, we get the key and the corresponding value. ### Key Concepts and Takeaways * Use the `for` loop for general-purpose looping. * Use the `range` loop for iterating over arrays, slices, strings, maps, and channels. * Be aware of the potential issues when modifying a slice or map while iterating over it. * The order of iteration over a map is unpredictable. ### Practice Exercise Write a Go program that uses the `range` loop to iterate over an array of strings and print the length of each string. **Commit Message:** Implemented practice exercise for range loop. ### Additional Resources * The Go Tour: [Flow control](https://tour.golang.org/flowcontrol/1) * Go By Example: [Loops](https://gobyexample.com/loops) **Leave a comment below if you have any questions or need help with the practice exercise.** Next topic: **Creating and using functions: parameters, return values, and multiple returns**.