And—Returns false. obj is always evaluated as it is the argument to a method call—there is no short-circuit evaluation in this case.

Exclusive Or—If obj is nil or false, returns false; otherwise, returns true.

Always returns the string "nil".

call_seq:

  nil.nil?               => true

Only the object nil responds true to nil?.

Always returns an empty array.

   nil.to_a   #=> []

Always returns zero.

   nil.to_f   #=> 0.0

Always returns zero.

   nil.to_i   #=> 0

Always returns the empty string.

Or—Returns false if obj is nil or false; true otherwise.