Clojure Lazy Sequences — Infinite Data, Zero Cost | Episode 12

What if a sequence had no end? With lazy evaluation, you only compute what you need. Infinite sequences cost nothing until you realize them. In this episode we explore range (finite and infinite), take, repeat, iterate, and take-while. We build powers of two, count from any starting point, and filter even numbers from infinity. Every operation is lazy — nothing runs until you ask for it. Student code: https://github.com/GoCelesteAI/clojure-for-beginners/tree/main/episode12 Every keystroke is shown on screen with generous pauses so you can follow along at your own pace. What You'll Learn: - range for finite and infinite counting sequences - take to grab N items from any sequence - repeat for infinite repetition - iterate to build sequences by repeated function application - take-while to stop at a condition - Why laziness means no wasted memory or computation - Output section headers for organized results Timestamps: 0:00 - Intro 0:12 - Preview: infinite data, zero cost 0:32 - Start the REPL 0:40 - range (finite and infinite) 0:58 - repeat 1:05 - iterate 1:19 - take-while 1:29 - Exit REPL 1:34 - Write lazy.clj in Neovim 1:55 - range section with output headers 2:40 - repeat and iterate section 3:49 - take-while section 4:32 - laziness with filter section 4:48 - Run with :!clj -M % 4:53 - Output explained line by line 5:48 - Review 5:58 - Recap 6:33 - What's next: Episode 13 Key Takeaways: 1. range gives finite or infinite counting. take controls how much you realize. 2. iterate builds a chain by applying a function repeatedly from a start value. 3. take grabs by count, take-while grabs by condition. 4. Laziness means infinite sequences use zero memory up front — only what you ask for gets computed. Next up — Episode 13: Destructuring. Taught by CelesteAI. Like and subscribe for more Clojure tutorials!