consp
object ⇒ generalized-boolean
object | an object. |
generalized-boolean | a generalized boolean. |
(consp nil) ⇒ false
(consp (cons 1 2)) ⇒ true
The empty list is not a cons, so
(consp '()) ≡ (consp 'nil) ⇒ false
(consp object) ≡ (typep object 'cons) ≡ (not (typep object 'atom)) ≡ (typep object '(not atom))