anchor.diff:  ;; (defun make-comparison-expr (field value)
   ;;   (list 'equal (list 'getf 'cd field) value))
   
  -(defun make-comparison-expr (field value)
  -  `(equal (getf cd ,field) ,value))
  -
  -(defun make-comparison-list (fields)
  -  (loop while fields
  -       collecting (make-comparison-expr (pop fields) (pop fields))))
  -
  -(defmacro where (&rest clauses)
  -  `#'(lambda (cd) (and ,@(make-comparison-list clauses))))
  -
   ;;Test query
   ;;(select (where :artist "Dixie Chicks"))
   ;; (select (where :title "Test"))
  
positive.code: ;; (select (where :rating 7))
  ;; (select (where :ripped t))
  
  (defun update (selector-fn &key title artist rating (ripped nil ripped-p))
    (setf *db*
  	(mapcar
  	 #'(lambda (row)
  	     (when (funcall selector-fn row)
  	       (if title    (setf (getf row :title) title))
  	       (if artist   (setf (getf row :artist) artist))
  	       (if rating   (setf (getf row :rating) rating))
  	       (if ripped-p (setf (getf row :ripped) ripped)))
  	     row) *db*)))
  
  ;;update test
  ;;(update (where :artist "Angelo") :title "angelo_title")
  
  
  (defun delete-rows (selector-fn)
    (setf *db* (remove-if selector-fn *db*)))
  
  
  ;;test where macro
  ;;(select (where :title "Home" :ripped t))
  
negative.code: (defvar *db* nil)
  
  
  (defun make-cd (title artist rating ripped)
    (list :title title :artist artist :rating rating :ripped ripped))
  
  
  (defun add-record (cd) (push cd *db*))
  
  
  (defun dump-db ()
    (dolist (cd *db*)
      (format t "~{~a:~10t~a~%~}~%" cd)))
  
  
  (defun prompt-read (prompt)
    (format *query-io* "~a: " prompt)
    (force-output *query-io*)
    (read-line *query-io*))
  
  
  (defun prompt-for-cd ()
    (make-cd
  