Clojure Seq Abstraction — One Interface for Every Collection | Episode 11

You've learned vectors, lists, maps, and sets. Now one abstraction ties them all together — the sequence. In Clojure, seq converts any collection into a uniform interface. Learn first and rest once, and they work on everything. In this episode we call seq on all five types, use first and rest across collections, and write a single function that handles vectors, lists, and strings with the same code. Student code: https://github.com/GoCelesteAI/clojure-for-beginners/tree/main/episode11 Every keystroke is shown on screen with generous pauses so you can follow along at your own pace. What You'll Learn: - seq converts any collection to a sequence (or nil if empty) - first and rest work on vectors, lists, maps, sets, and strings - Maps become sequences of key-value pairs - Strings become sequences of characters - seq on empty returns nil — the idiomatic emptiness test - Writing polymorphic functions that work on any seqable type Timestamps: 0:00 - Intro 0:12 - Preview: one interface for everything 0:32 - Start the REPL 0:40 - seq on vectors, lists, maps, sets, strings 1:11 - seq on empty returns nil 1:17 - first and rest on different types 1:45 - Exit REPL 1:50 - Write seqs.clj in Neovim 2:12 - seq section — all five types 3:25 - first and rest section 4:20 - describe-coll — one function, every type 5:42 - Run with :!clj -M % 5:46 - Output explained line by line 6:42 - Review 6:52 - Recap 7:27 - What's next: Episode 12 Key Takeaways: 1. seq converts any collection to a sequence. first and rest work on all of them. 2. Maps become pairs, strings become characters — everything is seqable. 3. seq on empty returns nil — use (when (seq coll) ...) as the idiomatic emptiness test. 4. Write one function and it handles every collection type — that's the power of the seq abstraction. Next up — Episode 12: Lazy Sequences. Taught by CelesteAI. Like and subscribe for more Clojure tutorials!