Question

I try to run this code in clisp:

(defun gen-world
(loop for x to *hight*
    do (loop for y to *width*
        do (acons '(x . y) '(rock) *world*))))

And get the following error:

*** - APPLY: argument list given to SYSTEM::ERROR-OF-TYPE is dotted
  (terminated by
   "Invalid specialized parameter in method lambda list
   (LOOP FOR X TO *HIGHT* DO
    (LOOP FOR Y TO *WIDTH* DO (ACONS '(X . Y) '(ROCK) *WORLD*))): (LOOP FOR Y IN
      *WIDTH* DO (ACONS '(X . Y) '(ROCK) *WORLD*))"
   )

When I run

(acons '(x . y) '(rock) *world*)

I get no errors

Why do this happen?
EDIT: *hight* *width* and *world* are global and in scope. *world* is a list.

Answer 1

I can see two problems here.

1. You are missing an argument list, so the LOOP form is taken as the argument list instead. And it happens to contain a dotted pair (X . Y) which is not allowed.
2. Your key is a constant '(X . Y) when you probably wanted a pair containing the (integer) values of X and Y.

Try this:

(defun gen-world ()
    (loop for x to *hight*
        do (loop for y to *width*
            do (acons `(,x . ,y) '(rock) *world*))))