Says who?

irb(main):001:0> class Fixnum

irb(main):002:1> def doit

irb(main):003:2> puts "hey"

irb(main):004:2> end

irb(main):005:1> end

=> nil

irb(main):006:0> 2.doit

hey

=> nil

irb(main):007:0>

Yup. Perhaps he was thinking of Python, where his assertion is true.

Not true in Python either since new-style classes unified types and classes.

  class Fixnum
    def +(other)
      42
    end
  end

3 + 2 => 42

I try to sneak this into all of my rubygems

Ah The Answer. BTW, it crashes my IRB (Ruby 1.9.1/Win)

You're partly right. Fixnums don't have a metaclass (or virtualclass) because they're actually "immediate". So you can't say 123.extend(Something) because 123 isn't really a full Object.

That's just to say that there aren't multiple "2"s. But 2 itself is still an object, pointing at its Fixnum class, which has all the normal Class and Object semantics.

Fixnums have a different representation in the interpreter (at least in 1.8 MRI) than normal objects do, which is probably what tripped me up here.

Yeah. Conceptually, you can think of the difference as whether or not there can be two copies of something. There can only be one copy of a Symbol, Fixnum, true, false, and nil. This means that true == true, and true.dup #=> error.