jonahisadev/lispy

A toy programming language with a LISP dialect

Lispy

Lispy is a toy programming language. It is an interpreted language, and uses a LISP-like dialect. I mostly wrote this as a proof-of-concept and as a challenge to myself.

I am publishing it publicly on GitHub for portfolio purposes, as well as educational for anyone who may come across it. I would of course not recommend that anyone seriously use it for anything other than playing around or learning.

If you like the idea of using a LISP-style programming language, please take a look at Clojure.

How to use

For information regarding the "core library" please visit docs/core.md.

Building

$ mkdir .build
$ meson setup .build
$ cd .build && ninja

You should have an executable called lisp ready to use!

Basic Usage

Running lisp will open a REPL where you can write Lispy code. State is maintained throughout the session until an EOL (Ctrl+D) signal is sent to the program, at which point it will exit.

Here are some example inputs to help you get started:

(+ 1 2)
;; => 3

(defn square [x] (* x x))
(square 5)
;; => 25

(defn sum [a b] (+ a b))
(sum 12 30)
;; => 42

(defn square [x] (* x x))
(map square [1 2 3])
;; => [ 1 4 9 ]

(defn more_than_one_digit [n] (> n 9))
(filter more_than_one_digit [4 9 18 42 3])
;; => [ 18 42 ]

(filter more_than_one_digit (map square [1 2 3 4 5]))
;; => [ 16 25 ]

(def the_answer 42)
(if (= the_answer 42) (true) (false))
;; => true

Right now, the interpreter does not allow multiline input. I may add that in the future because the below program is about as complex as one can reasonably program in one line. Also loading a file would be nice.

(defn game [guess answer] (if (= answer guess) (0) (if (> guess answer) (1) (-1))))
(game 50 42)
;; => 1 (too high)
(game 24 42)
;; => -1 (too low)
(game 42 42)
;; => 0 (just right!)

Summary

There are some cool things that the interpreter can do! This is due to the fact that the parser is really easy to build because of the simplistic nature of LISP-style code, but also because everything is just a stack. Outside of a key- value store for globals, it's all the stack. Which makes it super easy to reuse code all over the place because you really only need one implementation everywhere.