I've implemented my own Lisp on top of node.js, I can run s-expressions like this:
(assert (= 3 (+ 1 2))) (def even? (fn [n] (= 0 (bit-and n 1)))) (assert (even? 4)) (assert (= false (even? 5)))
Now I would like to add macros - the defmacro function - but this is where I'm stuck. I'm wondering how macro systems are implemented in other Lisps but I couldn't find many pointers (apart from this and this).
I've looked at the Clojure macro system - the Lisp I'm most familiar with - but that seemed too complicated and I couldn't find additional clues that I can readily apply (Clojure macros ultimately compile to byte code which doesn't apply to javascript, also I couldn't make sense of the macroexpand1 function.)
So my question is: given a Lisp implementation without macros but with an AST, how does one add a macro system like Clojure's macro system? Can this macro system be implemented in Lisp, or does it require extra features in the implementation in the host language?
One additional remark: I haven't implemented quote (') yet because I couldn't figure out what kind of values should be in the returned list. Should it contain AST elements or objects like Symbol and Keyword (the latter being the case for Clojure)?