In Common Lisp, false values are represented by the empty list –
() – or the symbol
These values can be quoted or unquoted.
;; Equivalent False Values () ; => NIL nil ; => NIL '() ; => NIL 'nil ; => NIL
All other values in Lisp represent truth.
There also exists the special constant symbol
t that is always equal to
t (and is therefore always true).
;; Some Different True Values 42 ; => 42 "this statement is false" ; => "this statement is false" t ; => T 't ; => T