From: Austin Ziegler <halostatue@...>
Date: 2005-08-12T03:57:38+09:00
Subject: Re: Namespace of method arguments (Ruby 2 Idea?)

On 8/11/05, rm_rails@cheapcomplexdevices.com
<rm_rails@cheapcomplexdevices.com> wrote:
> In the Programming Ruby book in the section of namespaces, I see the
> example:
> 
>    require "trig"
>    require "action"
>    y          =   Trig.sin(Trig::PI/4)
>    wrongdoing = Action.sin(Action::VERY_BAD)

> It seems very common to me to use constants from the module as
> parameters to the module - and rather uncommon to want constants from
> a different module as a parameer.

> Is there a reason why a method's arguments can't automatically include
> the namespace of the module the method came from so I could simply
> write:
> 
>    y          =   Trig.sin(PI/4)
>    wrongdoing = Action.sin(VERY_BAD)
> 
> and have it automatically look in the Trig namespace for the first PI
> and the Action namespace for VERY_BAD? I think this would make a lot
> of code that makes heavy use of constants look a lot cleaner; and
> perhaps encourage people to use constants more often rather than just
> magic numbers or strings or symbols as arguments.

Um.

1. Symbols aren't "magic"; they're effectively constants.
2. What if I have:

  require 'action'

  module VERY_BAD
    Action.sin(VERY_BAD)
  end

Obviously, this is, itself VERY_BAD if Action.sin does
  Action.sin Action::VERY_BAD
instead of using ::VERY_BAD which is, in this case, self. Why? Because
it means that if I *meant* to pass in ::VERY_BAD, I have to explicitly
specify it rather than relying on Ruby's constant lookup rules.

If Action is a *module*, then you have more flexibility:

  module Action
    def self.sin(my_sin)
      p my_sin
    end
    VERY_BAD = "I'm just drawn that way."
  end
  
  module VERY_BAD
    Action.sin(VERY_BAD) # => VERY_BAD
  end

  module VERY_BAD
    include Action
    Action.sin(VERY_BAD) # => "I'm just drawn that way."
  end

It's probably better to leave this alone.

-austin
-- 
Austin Ziegler * halostatue@gmail.com
               * Alternate: austin@halostatue.ca