[ruby-core:32132] Re: Ruby 2.0 Wiki/Wish-list?

On Sep 8, 2010, at 12:37 AM, Yukihiro Matsumoto wrote:

> Hi,
> 
> In message "Re: [ruby-core:32117] Re: Ruby 2.0 Wiki/Wish-list?"
>    on Wed, 8 Sep 2010 11:12:44 +0900, Joshua Ballanco <[e-mail]> writes:
> 
> |-- "def" returns a lambda instead of nil
> 
> "def" defines a method, which is slightly different in Ruby, so that
> returning a lambda would not be a good choice.  Some suggested to make
> "def" to return a symbol of the defining method.

This seems like a good place to start.

> |-- adding parens "()" to a lambda has the effect of calling it (i.e. my_lambda.() --> my_lambda() )
> 
> I have tried but couldn't make it possible.  If you have an idea, I am
> open to hear.

I don't yet, but I will take this as a personal challenge!

> |-- named parameters
> 
> Keyword arguments will be available on 2.0.

Excellent. Looking forward to that.

> 
> |-- full access to subclass from metaclasses (i.e. allow prototype-style inheritance)
> |-- true namespacing (i.e. adding a layer to const lookup without adding a class/metaclass)
> 
> I have no idea on above two.  Could you elaborate?

Sure.

-- full access to subclass from metaclasses

Essentially, I'd like to be able to do the following:

>> a = 'hello, world'
=> "hello, world"
>> class<<a
>>   def my_awesome_method
>>     self.length ** 2
>>   end
>> end
=> nil
>> a.my_awesome_method
=> 144
>> a.class
=> String
>> b = a.singleton_class.new
=> ""
>> b.class
=> String
>> b << 'test'
=> "test"
>> b.my_awesome_method
=> 16

As it is now, calling "a.singleton_class.new" raises an error. The idea of doing this would be to create a new object with all the same methods but without copying the properties. i.e. Prototype-based inheritance. The key, here, is that we can add methods to an instance of a class, and create new instances of that class without needing to create a subclass just to do so. I feel that, used properly, this feature might reduce some of the "polution" of core types that certain Ruby libraries suffer from, as people would be less tempted to open core classes just to add a few methods.


-- true (or, let's call it "lightweight") namespacing

A very common idiom in Ruby today is to pull all of the classes/modules of a project inside an "umbrella" module like so:
---
> cat my_first_class.rb
module MyModule
  class MyFirstClass
    def a_method
      ...
    end
  end
end

> cat my_second_class.rb
module MyModule
  class MySecondClass
    def another_method
      ...
    end
  end
end
---
There are two problems I see with this approach. First, the programmer is creating *and* reopening a module, perhaps many times, just to gain a level of scope. This module is not intended to be used as a mix-in, so all of the internal datastructures and mechanisms that enable mixing-in need to be set-up, but they are never used. Second, in the results of Object#constants there will be an entry for MyModule, but again MyModule is only being used to add a layer of scope. So, what I would like is a "namespace" keyword which adds to the constant resolution chain, but does not actually create a module for mix-ins and does not appear as an independent constant. It is lightweight in that it is only affecting lookup. Also, when someone does not want to have to always type "MyModuleName::MyClassName", currently the only option is to do "include MyModuleName", but this is doing a mix-in when all the programmer wanted to do was to remove a layer of constant resolution.

Cheers,

Josh