From: Gary Wright <gwtmp01@...>
Date: 2011-01-03T05:32:01+09:00
Subject: Re: 1.respond_to? :define_singleton_method # => true


>> Does anyone understand why Fixnum objects list this method but denies
>> knowing of it, when they are sent the message?
>> 
> 
> it's prolly to protect the coolness of integers & stuff, as from what i
> understand all the basic integers are pre-defined & immutable.

Fixnums are not 'immutable' in that you can associate state with a Fixnum instance and change that state:

class Fixnum
  attr_accessor :note
end

1.note = "the loneliest number"
1.note = "the second natural number"

The essential properties of a fixnum, the 'oneness' of 1, the 'twoness' of 2, are immutable in that those properties are associated with the unique identity of each fixnum instance and not with any state associated with the instance.

It is my understanding that the prohibition on singleton methods is because there doesn't seem to be an efficient way to implement them for objects that are implicitly represented by their object id (fixnum, symbol, nil, true, false).

Gary Wright