Tlen Lisp _verified_ ❲Real — 2027❳

(defn add [x : Int, y : Int] -> Int (+ x y)) But this also works:

I’ll admit it — I’m a sucker for Lisp dialects. Over the years, I’ve spent countless hours with Common Lisp, Clojure, Racket, and even Emacs Lisp (begrudgingly, at times). So when I stumbled across Tlen Lisp — whose name comes from the Polish word for “oxygen” — I was curious. Another Lisp? Really? tlen lisp

(let !counter 0 (each! [1 2 3] (fn [x] (set! counter (+ counter x)))) counter) ;; returns 6 The ! is a visual signal — no hidden side effects. Type systems are great, but they can interrupt flow. Tlen introduces soft types — optional, gradual, and runtime-erasable . You can add them when you need confidence, ignore them when prototyping. (defn add [x : Int, y : Int]