CODEWITHSUNDEEP
common-lisp
Fnifni
Fnifni

Reputation: 333

Macro : How to output a comma in a backquoted generated code?

I have a macro of the form:

;; Macro which does a sort of defun for instance, with some other stuff.
(defmacro def2 (name (&rest args) &body body)
  `(defun ,(intern (string-upcase name)) (,@args)
     ,@body))

And I want to generate lots of def2 :

(defmacro defdefs ()
  `(progn
     ,@(loop for name in '("name1" "name2" "name3")
         collect `(def2 ,name (&rest args)
            (print ,@args))))) ; <---- HERE.

I want to refer to the args in the def2 form, but if I write ,@args it will refer to a variable (not defined) in defdefs macro. I have thought to use something like macro-function and apply but is there a better way to tell defdefs that I want to output this list : (print ,@args) without evaluating the ,@args part during macroexpansion?

I have tried to play with quotes, double quotes, backquotes and double backquotes but I cannot find a solution...

Thank you in advance.

Upvotes: 2

Views: 113

Answers (1)

Rainer Joswig
Rainer Joswig

Reputation: 139251

CL-USER 33 > (defmacro def2 (name (&rest args) &body body)
               `(defun ,(intern (string-upcase name)) (,@args)
                  ,@body))
DEF2

CL-USER 34 > (defmacro defdefs ()
               `(progn
                  ,@(loop for name in '("name1" "name2" "name3")
                          collect `(def2 ,name (&rest args)
                                     (print args)))))
DEFDEFS

CL-USER 35 > (pprint (macroexpand '(defdefs)))

(PROGN
  (DEF2 "name1" (&REST ARGS) (PRINT ARGS))
  (DEF2 "name2" (&REST ARGS) (PRINT ARGS))
  (DEF2 "name3" (&REST ARGS) (PRINT ARGS)))

CL-USER 36 > (pprint (macroexpand-1 '(DEF2 "name1" (&REST ARGS) (PRINT ARGS))))

(DEFUN NAME1 (&REST ARGS)
  (PRINT ARGS))

Upvotes: 4

Related Questions