From: dblack@...
Date: 2006-03-27T01:17:10+09:00
Subject: Re: Noob: use of the double colon

Hi --

On Mon, 27 Mar 2006, ara.t.howard@noaa.gov wrote:

> On Sun, 26 Mar 2006 dblack@wobblini.net wrote:
>
>>> Bothe seem to work OK.
>>> Is there a difference? If yes, what is the difference?
>> 
>> They do both work.  I've never understood why the :: exists for this
>> purpose, since the . is the normal way of sending messages to objects
>> and works perfectly well whether or not the receiver is a class.  It's
>> on my very short list of things I'd like to see removed from Ruby.
>
> i think it's quite useful in the context of metaprogramming or classes or
> modules as variables:
>
>  m = method_returning_an_module
>  m::module_method
>
>  c = method_returning_an_class
>  c::class_method
>
>  o = method_returning_an_object
>  o.object_method
>
> i find this approach helps me understand which kind of thing my variables 
> have
> at a quick glance.  it's a similar idea to naming arrays with plural words
>
>  people = []
>  person = people.first
>
> which some hate and some love.

Does anyone hate calling a variable person? :-)

> still, these kinds of techniques can reduce the need for comments
> and preserve programmer sanity.

I honestly don't see any connection between the two techniques (:: and
suggestive variable names).  c::meth doesn't communicate anything to
me about c.  Even if it did, I'm not sold on the idea that it's
necessary to have a different message-sending operator for a
particular class of objects.  It doesn't scale: you can come up with
lots of variable names (my_class, etc.), but you can't keep adding
operators to make distinctions among receivers.  Nor is it necessarily
vital in very many cases to make such distinctions.

And when it's a matter of String.new vs. String::new, you already know
it's a class anyway :-)


David

-- 
David A. Black (dblack@wobblini.net)
Ruby Power and Light, LLC (http://www.rubypowerandlight.com)

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