Clojure in 5 Minutes: Install, REPL & First Function | Ep 1

Learn Clojure from scratch — in Neovim! In this first episode, we install Clojure, start the REPL, evaluate our first expressions, then write and run a real .clj file. By the end, you'll have a working Clojure setup and your first function. Clojure is a modern Lisp on the JVM with a REPL-driven workflow, immutable data, and world-class concurrency. This series takes you from zero to a deployed web app — 45 episodes across 9 phases. No prior Lisp or functional programming experience required. Student code: https://github.com/GoCelesteAI/clojure-for-beginners/tree/main/episode01 Every keystroke is shown on screen with generous pauses so you can follow along at your own pace. What You'll Learn: - Installing Clojure on macOS, Linux, and Windows - Verifying the install with clj --version - Starting the Clojure REPL and evaluating expressions - Prefix notation: (+ 1 2 3) instead of 1 + 2 + 3 - Defining a function with defn — and why the last expression returns - Using str, count, and nested forms - Writing hello.clj and running it with :!clj -M % - Exiting the REPL cleanly with Ctrl+D - Editing and rerunning with /search and ciw in Neovim Install Commands: - macOS: brew install clojure/tools/clojure - Linux: curl -O https://download.clojure.org/install/linux-install.sh && chmod +x linux-install.sh && sudo ./linux-install.sh - Windows: iwr -useb download.clojure.org/install/win-install.ps1 | iex Timestamps: 0:00 - Intro 0:12 - Install Clojure (macOS / Linux / Windows) 0:22 - Run brew install live + clj --version 0:43 - Start the REPL 0:47 - Evaluate expressions (println, +, *, nested, str, count) 1:15 - Exit the REPL with Ctrl+D 1:20 - Write hello.clj in Neovim 1:41 - First println in a file 1:54 - Define greet with defn 2:15 - Call greet with World 2:29 - One more line — print two plus three 2:44 - Run with :!clj -M % 2:49 - Output explained line by line 3:19 - Tweak and rerun 3:36 - Second output explained 3:59 - Recap: prefix notation, defn, REPL-first 4:19 - What's next — Episode 2 Key Takeaways: 1. Prefix notation is the one syntactic rule in Clojure — function first, arguments follow 2. defn defines a function; the last expression in the body is the return value 3. The REPL is where Clojure lives — evaluate instantly with clj, run files with :!clj -M % Series Roadmap: - Episodes 1-6: REPL & first values - Episodes 7-13: Collections & sequences - Episodes 14-19: Functional core (map, filter, reduce, threading, transducers) - Episodes 20-24: Namespaces, projects, deps.edn, testing - Episodes 25-30: State & concurrency (atom, ref, agent, core.async) - Episodes 31-35: Data modeling (spec, malli, protocols, multimethods) - Episodes 36-38: Macros & metaprogramming - Episodes 39-41: Java interop, Babashka, uberjars - Episodes 42-45: Capstone — Ring + Reitit + next.jdbc + Docker Next up — Episode 2: S-Expressions & Syntax. Taught by CelesteAI. Like & subscribe for more Clojure tutorials!