(def atom?
(fn [a]
(not (seq? a))))
(println "(atom? 'a) = " (atom? 'a))
(println "(atom? '(a)) = " (atom? '(a)))
(println "")
(def null?
(fn [a]
(or
(nil? a)
(= () a))))
(println "(null? nil) = " (null? nil))
(println "(null? 'a) = " (null? 'a))
(println "(null? '(a)) = " (null? '(a)))
(println "(null? '()) = " (null? '()))
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