NilClass

The class of nil. nil is the sole instance of this class, signifying FALSE along with the false object. All other objects are true.

Superclass

self & other: Always returns false.
self | other
self ^ other: If other is true, returns true; if false, returns false.
nil?: Always returns true.
to_a: Returns the empty array [].
to_f: Returns 0.0.
to_i: Returns 0.
to_s: Returns the empty string "".