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Code: Select all

;;; The code below shows a problem I'm having when trying to invoke a macro
;;; that accepts a list as one of the parameters while inside a LOOP.

;; Here is a sample macro.  It generates a class and associated stream-formatter
;; based on the NAME and SLOT-LIST parameters.

(defmacro create-class-and-printer (class slot-list)
  `(progn
     (defclass ,class () 
       ,(loop for (slot value) in slot-list
	   collect (list slot :initform (string value))))
     (defmethod print-object ((obj ,class) stream)
       (format stream "~{~a ~}" (loop for (slot nil) in 'slot-list
				    collect (slot-value obj slot))))))

;; If I invoke the macro directly, it works just fine.

(create-class-and-printer spanish-dictionary ((one uno) (two dos) (three tres)))

;; But if I try to invoke the macro while iterating through a list, it appears
;; to have trouble with the slot-list parameter, and doesn't recognize it as a
;; LIST, but printing the type shows it as a CONS.

(let ((language-list '((spanish-dictionary ((one uno) (two dos) (three tres)))
		       (french-dictionary ((one un) (two deux) (three trois)))
		       (german-dictionary ((one ein) (two zwei) (three drei)))
		       (japanese-dictionary ((one ichi) (two ni) (three san))))))
  (loop for (language dictionary) in language-list
     do (format t "Dictionary is type: ~a~%" (type-of dictionary))
     do (format t "Value of Dictionary is: ~a~%" dictionary)
     do (format t "Is this a list? ~a~%" (listp dictionary))
     do (create-class-and-printer language dictionary)))


;; I think this might have something to do with macro parameters being
;; "destructured" but am not clear on how to resolve it.  My google searches
;; haven't turned up much, which either means I'm doing something extremely
;; dumb, extremely rare, or a combination of the two.

Code: Select all

(defmacro create-class-and-printer (class slot-list)
  `(progn
     (defclass ,class ()
       ,(loop for (slot value) in slot-list
              collect (list slot :initform (string value))))
     (defmethod print-object ((obj ,class) stream)
       (format stream "~{~a ~}" (loop for (slot nil) in ',slot-list
                                      collect (slot-value obj slot))))))

(defmacro list-create-class-and-printer (list)
  `(progn ,@(loop for (language dictionary) in list
                  collect `(create-class-and-printer ,language ,dictionary)
                  do (format t "Dictionary is type: ~a~%" (type-of dictionary))
                  do (format t "Value of Dictionary is: ~a~%" dictionary)
                  do (format t "Is this a list? ~a~%" (listp dictionary)))))

(list-create-class-and-printer
 ((spanish-dictionary ((one uno) (two dos) (three tres)))
  (french-dictionary ((one un) (two deux) (three trois)))
  (german-dictionary ((one ein) (two zwei) (three drei)))
  (japanese-dictionary ((one ichi) (two ni) (three san)))))