chao

A small Lisp interpreter.

Syntax

• Values: nil, booleans, integers, floats, strings, symbols, and lists.
• Quote: 'expr returns expr as data.
• Quasiquote: a backtick-prefixed expression returns an expression template.
• Unquote: ,expr evaluates expr inside a quasiquote.

Forms

Form	Description	Example
lambda	Create an anonymous function	(lambda (x) (* x x))
def	Define a variable	(def answer 42)
def	Define a function	(def square (x) (* x x))
set	Assign an existing binding	(set answer 43)
if	Evaluate one branch lazily	(if true "yes" "no")
list	Build a list	(list 1 (+ 1 1) 'x)
defmacro	Define a macro	(defmacro when (c b) `(if ,c ,b nil))
intern	Convert a string to a symbol	(intern "name")
+ - * /	Arithmetic operators	(+ 1 (/ 4 2.0))
= < >	Comparison operators	(= 1 2)

def creates or replaces a binding. set updates an existing binding and errors when the name is unbound.

Macros

Macros receive raw syntax and return an expression that is evaluated in the caller's environment.

(defmacro when (cond body) `(if ,cond ,body nil))
(when true (+ 1 2))

Building

1. Install rust
2. git clone https://github.com/lukad/chao.git
3. cd chao
4. cargo build --release