Common Lisp treats any non-nil value as "true," so the behavior is not bad for the "and" macro (yes, it is a macro). Additionally, the standard says that "and"

Common Lisp treats any non-nil value as "true," so the behavior is not bad for the "and" macro (yes, it is a macro). Additionally, the standard says that "and" should evaluate to nil if any argument evaluates to nil, or to its last argument otherwise: http://www.lispworks.com/documentation/HyperSpec/Body/m_and.htm http://www.lispworks.com/documentation/HyperSpec/Body/m_and....