Welcome back! You're about to dive into an essential part of controlling the flow of your Clojure programs: conditionals. You have built a foundation with the basics of Clojure, and now we are going to expand on that by learning how to make decisions within your programs. This will help you add logic and control, making your programs more robust and dynamic.

Conditionals allow you to execute different pieces of code based on whether certain conditions are true or false. This unit will cover various forms of conditional expressions in Clojure:

1. if: Executes a block of code if a condition is true, and another block if it's false.
2. if-not: Executes a block of code if a condition is false, and another if it's true.
3. cond: Allows for multiple conditions and corresponding actions.
4. when: Executes a block of code only if a condition is true.
5. when-not: Executes a block of code only if a condition is false.

We'll apply these conditionals using a simple example involving a hero's health status in a game.

Here's a quick peek at what you'll be able to do after completing this unit:

Clojure
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1(def hero-health 80)
2
3(if (> hero-health 50)
4  (println "Hero is in good shape!")
5  (println "Hero needs healing!"))
6
7(if-not (> hero-health 50)
8  (println "Hero needs healing!")
9  (println "Hero is in good shape!"))
10
11(cond
12  (> hero-health 75) (println "Hero is in excellent shape!")
13  (> hero-health 50) (println "Hero is in good shape!")
14  (> hero-health 25) (println "Hero is in poor shape!")
15  :else              (println "Hero needs immediate healing!"))
16
17(when (> hero-health 50)
18  (println "Hero is in good shape!"))
19
20(when-not (> hero-health 50)
21  (println "Hero needs healing!"))

In this example, the message changes based on the value of hero-health. Note that this example uses comparison operators like (>) to evaluate conditions; these will be covered in depth later in this course.

Mastering conditionals is crucial because they enable your program to make decisions, adding dynamic behavior based on different inputs and states. For instance, imagine a game's hero whose health can vary. By using conditionals, you can create different messages based on the hero's health, enhancing user experience and interactivity.

Enhancing your code with conditionals will not only make it smarter but also more flexible. Ready to get started? Let's jump into the practice section.