From: Christoph <chr_mail@...>
Date: 2004-12-01T11:16:33+09:00
Subject: Re: singleton methods : when are they not permitted?

Florian Gross schrieb:

> itsme213 wrote:
>
>> Why no singleton methods on Symbol?
>>
>> Are there other objects that are also not allowed to have singleton 
>> methods?
>
>
> Singleton methods can not be defined for "immediate" Objects. 
> Immediate Objects are stored directly by their id which means they are 
> very cheap to use.
>
> Immediate objects include all Fixnums, Symbols, true, false and nil 
> (but note that def true.foo; end will silently add the method directly 
> to TrueClass because there is guaranteed to be only one instance, 
> true, for it.)
> You can also not add methods to Floats and Bignums (this is for 
> consistency with Fixnums), but this can be changed by overriding 
> Numeric#singleton_method_added

(Miss)Applying syllogistic logic you can add singleton methods
to Floats or Singletons you just have do deal with the exception
either by changing Numeric#singleton_method_added or simply
catching the exception

x = 2.0
class << x
def bla;end
rescue
end

x.bla

/Christoph