**Course Title:** Kotlin Programming: From Basics to Advanced Techniques **Section Title:** Control Structures and Functions **Topic:** Loops: for, while, do-while ### Introduction to Loops In the previous topic, we discussed conditional statements, which allow your program to make decisions based on certain conditions. However, there are situations where you want to execute a block of code repeatedly, either a fixed number of times or until a certain condition is met. This is where loops come in. Loops are control structures that enable you to execute a block of code repeatedly, either for a specific number of iterations or until a certain condition is met. In this topic, we'll explore the three types of loops in Kotlin: `for`, `while`, and `do-while`. ### For Loops A `for` loop is used to execute a block of code for a fixed number of iterations. It takes an iterable (such as an array, list, or range) and assigns each element to a variable, allowing you to access and manipulate the values in the iterable. **Syntax:** ```kotlin for (variable in iterable) { // code to execute } ``` **Example:** ```kotlin val numbers = listOf(1, 2, 3, 4, 5) for (number in numbers) { println(number) } ``` **Output:** ``` 1 2 3 4 5 ``` In this example, the `for` loop iterates over the `numbers` list and assigns each element to the `number` variable. Inside the loop body, we print the `number` variable to the console. **Range-Based For Loops** Kotlin also supports range-based `for` loops, which allow you to iterate over a range of numbers. **Syntax:** ```kotlin for (variable in start..end) { // code to execute } ``` **Example:** ```kotlin for (i in 1..5) { println(i) } ``` **Output:** ``` 1 2 3 4 5 ``` ### While Loops A `while` loop is used to execute a block of code while a certain condition is true. The loop body is executed repeatedly until the condition becomes false. **Syntax:** ```kotlin while (condition) { // code to execute } ``` **Example:** ```kotlin var i = 0 while (i < 5) { println(i) i++ } ``` **Output:** ``` 0 1 2 3 4 ``` In this example, the `while` loop continues to execute the loop body as long as `i` is less than 5. Inside the loop body, we print the `i` variable to the console and increment it by 1. ### Do-While Loops A `do-while` loop is similar to a `while` loop, but the loop body is executed at least once before the condition is checked. **Syntax:** ```kotlin do { // code to execute } while (condition) ``` **Example:** ```kotlin var i = 0 do { println(i) i++ } while (i < 5) ``` **Output:** ``` 0 1 2 3 4 ``` In this example, the `do-while` loop executes the loop body at least once before checking the condition. Inside the loop body, we print the `i` variable to the console and increment it by 1. ### Key Concepts and Practical Takeaways * Loops allow you to execute a block of code repeatedly, either for a fixed number of iterations or until a certain condition is met. * `for` loops are used to iterate over iterables or ranges. * `while` loops are used to execute a block of code while a certain condition is true. * `do-while` loops are used to execute a block of code at least once before checking the condition. ### Conclusion In this topic, we covered the three types of loops in Kotlin: `for`, `while`, and `do-while`. We explored the syntax and examples of each loop type and discussed key concepts and practical takeaways. **What's Next?** In the next topic, we'll cover defining and invoking functions in Kotlin, including parameters, return types, and more. **External Resources:** * [Kotlin Documentation: Loops](https://kotlinlang.org/docs/control-flow.html#loops) * [Kotlin Tutorial by Example: Loops](https://play.kotlinlang.org/byExample/05_loops) **Leave a comment or ask for help:** If you have any questions or need help with the material, feel free to leave a comment below.