```ruby
module Kernel

  def Bignum(arg)
    Integer(arg)
  end

  def Fixnum(arg)
    Integer(arg)
  end

  def NilClass(arg)
    nil
  end

end
```

Revert "Fix Ruby 1.8 incompatibility"
user
```ruby
module Kernel

  def Bignum(arg, base=0)
    Integer(arg, base)
  end

  def Fixnum(arg, base=0)
    Integer(arg, base)
  end

  def NilClass(arg)
    nil
  end

end
```
assistant