Lists comprehensions macro for lisp, and a pattern-matching macro

listcomprehension

(defmacro @ (value bind list test)
  (let ((newlist (gensym)))
    `(let ((,newlist nil))
       (dolist (,bind ,list)
         (when ,test
           (push ,value ,newlist)))
       (nreverse ,newlist))))

(defmacro pattern (bind l &rest body)
  `(destructuring-bind ,bind ,l
     ,@body))