This page demonstrates CodeMirror's OmetaJS parser.

Adapted from the official Javascript parser by Eric KEDJI <eric.kedji@gmail.com>.

// Source: http://www.tinlizzie.org/ometa-js/#Lisp // Inspired by McCarthy's meta-circular lisp ometa Lisp { ev = string:a -> self.env[a] | [#lambda :fs :body] -> [#lambda, fs, body] | [#quote :ans] -> ans | [#cond evCond:ans] -> ans | [ev:f ev*:xs] app(f, xs):ans -> ans, evCond = condF* condT:ans anything* -> x, condT = [ev:x ?x ev:ans] -> ans, condF = ~condT anything, app = #car [[:hd anything*]] -> hd | #cdr [[:hd anything*:tl]] -> tl | #cons [:hd :tl] -> [hd].concat(tl) | #atom [:x] -> (!(x instanceof Array)) | #eq [:x :y] -> (x == y) | [#lambda :fs :body] :args enter bind(fs, args) ev(body):ans leave -> ans, enter = -> (self.env = self.env.delegated({_p: self.env})), bind = [] [] | [:f anything*:fs] [:a anything*:as] bind(fs, as) -> (self.env[f] = a), leave = -> (self.env = self.env._p) } Lisp.initialize = function() { this.env = {car: "car", cdr: "cdr", cons: "cons", atom: "atom", eq: "eq", nil: null, T: "T"} } lispEval = function(x) { return Lisp.match(x, "ev") } lispEval([`quote, [1, 2, 3]]) lispEval([`car, [`quote, [1, 2, 3]]]) lispEval([`cdr, [`quote, [1, 2, 3]]]) lispEval([`cons, [`quote, `x], [`quote, `y]]) lispEval([`eq, [`quote, `x], [`quote, `x]]) lispEval([[`lambda, [`x], [`cons, `x, `x]], [`quote, `boo]])