In this section, we kick-start our journey into Clojure, exploring the foundational aspects of the language. As you're presumably familiar with object-oriented languages like Java, C++, Ruby, or Python, you'll find some aspects of Clojure quite refreshing and new. However, no prior knowledge of Java, Lisp, or Clojure is required. This section sets the stage for you to feel comfortable with the basics, so you’re ready to build upon this knowledge in subsequent sections.

Clojure is a modern, dynamic, and functional dialect of the Lisp programming language on the Java platform. What makes Clojure special is its emphasis on immutability and its powerful concurrency support. Its popularity stems from its simplicity and the way it enables developers to write concise, expressive code. Some of the most significant features of Clojure include:

• Immutability: Data structures are immutable by default, which leads to safer and more predictable code.
• First-class functions: Functions are first-class citizens and can be passed around and manipulated just like any other data.
• Concurrency: Provides robust support for concurrent programming with features like Software Transactional Memory (STM) and core.async.
• Interoperability: Seamlessly integrates with Java, leveraging Java's comprehensive ecosystem.

You can learn more about Clojure at the official Clojure website.

One of the first things you'll notice about Clojure is its distinctive syntax, which it inherits from Lisp. Here are some key points:

• Parentheses: Clojure code is written in a series of nested lists, denoted by parentheses. For example:

  Clojure
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  1(println "Hello, World!")

• Infix vs. Prefix notation: Unlike many languages that use infix notation (e.g., 1 + 2), Clojure uses prefix notation where the operator comes before the operands, like so:

  Clojure
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  1(+ 1 2 3)
  2(* 2 3 4)
  3(+ 1 (* 2 3))

• Function Calls: In Clojure, function calls are written in the form of lists. The first element in the list is the function, and all the other elements are arguments. For instance, (+ 1 2) is a call to the + function with 1 and 2 as arguments. Similarly:

  Clojure
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  1(println "Hello," "Clojure" "World!")

  In this example, println is the function, and "Hello,", "Clojure", and "World!" are the arguments.

In this unit, you'll:

1. Become familiar with Lisp syntax and conventions.
2. Learn how to print messages to the console using println.
3. Perform basic arithmetic operations like addition and multiplication.
4. Define and work with variables using the def keyword.
5. Concatenate strings using str function
6. Write comments to document your code.

Here's a quick example to illustrate these points:

Clojure
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1;; Game basics: printing messages, basic math, and defining variables
2
3(println "Hello," "Clojure", "World!")
4
5(def welcome-message "Welcome to the Clojure Shooter Game!")
6(println welcome-message)
7
8(def hero-score (+ 50 50 20)) ;; Adding score points, result is 120
9(def villain-damage (* 2 25)) ;; Calculating damage, result is 50
10
11;; More complex arithmetic operations
12(def complex-calculation-1 (+ 20 (* 30 2))) ;; Result is 80
13(def complex-calculation-2 (/ (+ 100 (* 5 2)) 2)) ;; Result is 55
14(def complex-calculation-3 (- 200 (/ 50 2))) ;; Result is 175
15
16;; String concatenation
17;; println concatenates with space between, while str concatenates directly
18(def concatenated-message (str "Your current score is " hero-score "!"))
19(println concatenated-message)

Understanding basic operations and how to define variables is crucial. These are the building blocks of programming in any language. Mastering these Clojure concepts will enable you to manipulate game elements such as scores, messages, and player statuses in our shooter game example. This knowledge forms the groundwork for everything else you'll encounter in Clojure, from controlling logic to handling data structures.

Ready to start coding? Let's move on to the practice section and solidify these concepts with hands-on exercises!