Thanks Matthias. I should have read the error message more carefully. For anyone who is interested, it has nothing to do with cons or mcons or quotes. There was a mistake in interpreter.rkt.
If you'd like to try finding it yourself, then stop reading. ... ... ... ... ... ... ... ... ... ... Here's the fix. In interpreter.rkt, under the definition of myeval, in the case of a let expression, it should have been: [(eq? (car expr) 'let) (eval-sequence (cddr expr) (extend-env (map first (second expr)) (eval-args (map second (second expr)) env) env))] -- You received this message because you are subscribed to the Google Groups "Racket Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to racket-users+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.