(ql:quickload :parenscript)
 
 (defpackage :parenscript-chaining
   (:use :cl :parenscript))
 
 (in-package :parenscript-chaining)
 
 (defclass promise ()
   ())
 (defgeneric then (promise cb))
 
 (defmacro+ps with-promise ((result-sym promise-form) &body body)
   (let ((promise-sym (gensym)))
     `(let* ((,promise-sym ,promise-form)
             ,@(loop for form in body
                     collect `(,promise-sym ((@ ,promise-sym then) (lambda (,result-sym) ,form)))))
        ,promise-sym)))
 
 
 (ps
   (with-promise (val (chain window (fetch "/http/google.com")))
     (chain val (json))
     (@ val "success")))