(defn stack-operations [stack]
  "Actions to take if (nil? stmt)"
  (comment 'If a left paren is found on the stack, it means
           that there was no right paren to match it, and
           therefore the statement had unbalanced parentheses.')
  (cond (and (not (nil? stack))
             (= (first stack) \()) (print "Unbalanced parentheses.\n")
        (nil? stack) '()
        :else (cons (first stack) (%shunting-yard '() (rest stack)))))

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