From: tamouse mailing lists <tamouse.lists@...>
Date: 2013-02-02T14:57:41+09:00
Subject: Re: Enumeration vs Enumerable

On Fri, Feb 1, 2013 at 11:07 PM, Arup Rakshit <lists@ruby-forum.com> wrote:
> Calvin B. wrote in post #1094821:
>> Hi,
>>
>> sorry if I confused you, I just repeated the definition (as I remembered
>> it) without really explaining it. In the case of an array, the array is
>> the enumeration AND the collection. There are some cases in which the
>> two differ. An example which hopefully clears that up: The collection of
>> all integers. Since the collection is infinite, we can't really have a
>> list of all integers (at least as data). We could, in this specific
>> case, describe our collection in a way so we can list an arbitrary
>> number of elements, but never all.
>>
>> Regards,
>> Calvin
>
> @calvin - Your example is good. But in this context with this example
> how array is differing from enumerator?

An Array is a class which includes the properties of Enumerable:

1.9.3-head :003 > Array.ancestors
 => [Array, Enumerable, Object, Kernel, BasicObject]

If the class Array was implemented in pure Ruby (which it's not), it
would look something like this:

class Array
  include Enumerable
  # class definition and overrides for Enumerable methods as needed3
end

The Enumerable class provides methods for many of the actions you
normally take on an Array, such as :each, :sort, :count, :first, and
so on. Other classes also include Enumerable; Hash, File, Dir, Range,
etc.