Question

I’m trying to pass a list to macro, for example:

(defmacro print-lst (lst)
  `(progn
     ,@(mapcar #'(lambda (x) `(print ,x)) lst)))
(let ((lst '(1 2 3)))
      (print-lst lst))

It caught error: “The value LST is not of type LST”.

So, my question is, what’s wrong with this piece of code and how to pass list to macro?

Answer 1

I’m not sure why you want to define this as a macro instead of a regular function, but the problem is that macros do not evaluate their arguments. If you give it the name of a lexical variable, all it sees is the name ('LST), not the bound value. It is complaining (correctly) that the symbol 'LST is not a list, and thus not a valid second argument to MAPCAR.

You could call it as (print-lst (1 2 3)), but then you could do without the macro and just do (mapc #'print lst)