From: ara.t.howard@...
Date: 2006-03-27T01:41:51+09:00
Subject: Re: Noob: use of the double colon

On Mon, 27 Mar 2006 dblack@wobblini.net wrote:

> 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.

it does though - you know c __must__ be a module (classes being modules).

> 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.

i can see that point of view.  still, i like this:

     harp:~ > cat a.rb
     module A
       module B
         module C
           class D; end
           E = 42
           def self::foo() 42 end
         end
       end
     end

     namespace = A::B::C

     p namespace::D
     p namespace::E
     p namespace::foo


     harp:~ > ruby a.rb
     A::B::C::D
     42
     42

and i think it's why '::' can call methods - though this is a w.a.g.


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

only sometimes though:


   module M
     class C
     end
   end

   def C(*a, &b) ::M::C::new(*a, &b) end

   C.new


this is contrived, but String is a perfect example of this: both String() and
String exist and certainly many libs export 'const methods'.

all you really when a variable starts with [A-Z] is that it's a const.  this
happends quite a bit in my code because i always wrap up code into modules so i
end up with things like this:

   module M
     module Logging
     end
     module Util
     end
     class A
       include Util
       include Logging
     end
     class B
       include Util
       include Logging
     end
     class C
       include Util
       include Logging
     end
     def self::new *a, &b
       C::new *a, &b
     end
   end

where 'C' is sort of the 'default' or 'main' class in this set - so i provide
a convenience method for the common ctor case.  of course you can use '.new'
here... i'm just pointing out that a lefthand side const may not be a class.


regards.

-a
-- 
share your knowledge.  it's a way to achieve immortality.
- h.h. the 14th dali lama