Hi Konstantinos. Welcome to Lisp!
How did you invoke objects-at?
I copied the relevant code from the book
(defparameter *objects* '(whiskey bucket frog chain))
(defparameter *object-locations* '((whiskey living-room)
(defun objects-at (loc objs obj-locs)
(labels ((at-loc-p (obj)
(eq (cadr (assoc obj obj-locs)) loc)))
(remove-if-not #'at-loc-p objs)))
Note: in general I recommend typing in code yourself when you are learning new stuff, and you may be doing that, but I wanted to make sure I got it right quickly and just copied it.
Then I ran:
(objects-at 'garden *objects* *object-locations*)
=> (FROG CHAIN)
So, two questions:
1. How are you invoking objects-at?
2. Did you double-check all the code?
We can also talk about how it works, if you want.
I’ve confused myself with both of those in previous learning experiences….
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