Can Fixnum/Float be nil?

Question

Can a Fixnum/Float be nil? Like can self even be nil in this case:

class Fixnum
  def clamp(min, max)
    if self == nil then nil end
    ...
  end
end

Answer 1

This is impossible because nil has its own class,NilClass:

irb(main):001:0> nil.class
=> NilClass
irb(main):002:0> 456.class
=> Fixnum

So a variable can either be a Fixnum or a NilClass but not both.

In the context of a class instance method, self always refers to the instance, which is of the type of the class.

Also self cannot be changed:

irb(main):006:0> class C
irb(main):007:1>   def z
irb(main):008:2>     self = nil
irb(main):009:2>   end
irb(main):014:1> end
SyntaxError: (irb):8: Can't change the value of self
self = nil
      ^
        from D:/dev/Ruby20/bin/irb:12:in `<main>'

Answer 2

No. Object is either kind of Fixnum or NilClass. self is always a type of the current class.

Answer 3

Nope. The only way self could possibly equal nil is if you're inside NilClass.

class NilClass
  def self_is_nil?
    self == nil
  end
end

nil.self_is_nil? # => true

Answer 4

Just ask Ruby:

nil.is_a? Fixnum
# false
nil.is_a? Float
# false