Janet

A functional and imperative Lisp and bytecode interpreter, where lists are replaced by other data structures (arrays, tables (hash table), struct (immutable hash table), tuples).

The language also supports bridging to native code written in C, meta-programming with macros, and bytecode assembly.

Website | Source | Janet for Mortals

It's like a "modern Lisp", featuring great and easy C interop and a variety of data types like arrays, structs, tables, etc.

Hello world:

(print "Hello, world!")

Object-oriented programming:

# Create a new object called Car with two methods, :say and :honk.
(def Car
 @{:type "Car"
   :color "gray"
   :say (fn [self msg] (print "Car says: " msg))
   :honk (fn [self] (print "beep beep! I am " (self :color) "!"))})

# Red Car inherits from Car
(def RedCar
 (table/setproto @{:color "red"} Car))

(:honk Car) # prints "beep beep! I am gray!"
(:honk RedCar) # prints "beep beep! I am red!"

# Pass more arguments
(:say Car "hello!") # prints "Car says: hello!"

(defn sum3
  "Solve the 3SUM problem in O(n^2) time."
  [s]
  (def tab @{})
  (def solutions @{})
  (def len (length s))
  (for k 0 len
    (put tab (s k) k))
  (for i 0 len
    (for j 0 len
      (def k (get tab (- 0 (s i) (s j))))
      (when (and k (not= k i) (not= k j) (not= i j))
        (put solutions {i true j true k true} true))))
  (map keys (keys solutions)))

(let [arr @[2 4 1 3 8 7 -3 -1 12 -5 -8]]
  (printf "3sum of %j: " arr)
  (printf "%j" (sum3 arr)))

Tags: language   lisp   native   windows   linux   macos  

Last modified 15 November 2025