[ruby-core:33375] Re: [Ruby 1.9-Feature#4085][Open] Refinements and nested methods

Hi,

Thank you for your reply!


2010/11/25 Shugo Maeda <[e-mail]>:
> However, I'm afraid that there are too many patches, some of which
> have been already reverted.

Please fair them :-)


>>  - Your patch adds `klass' to stack frame, which may cause
>>    big performance degradation.  We should check benchmark
>>    result (though I'm not so concerned).
>
> I have run "make benchmark" 5 times, and it shows that the modified
> version is slower than average 2.5% than the original version.

Sounds good!


>>  - API design.
> Because I'd like to allow multiple refinements in one module, for
> example, in the following case:
>
>  module MyXmlFormat
>    refine Integer do
>      def to_xml; ...; end
>    end
>
>    refine String do
>      def to_xml; ...; end
>    end
>
>    refine Hash do
>      def to_xml; ...; end
>    end
>    ...
>  end

After my short trial of this feature, I'd like an API to do
`refine' and `using' at once without explicit module, such as:

  using_refine(Fixnum) do
    def /(other) quo(other) end
  end

(equivalent to)

  using(Module.new do
    refine(Fixnum) do
      def /(other) quo(other) end
    end
  end)

Note that we cannot define `using_define' by ourselves because
of lexical scope limitation:

  def using_refine(klass, &blk)
    using(Module.new { refine(klass, &blk) })
  end

  using_refine(Fixnum) do
    def /(other) quo(other) end
  end

  p 1 / 2  #=> 0

I guess that this `using_refine' is useful itself (though its
name is arguable).  In addition, it allows us to write
MyXmlFormat as follows:

  module MyXmlFormat
    using_refine(Integer) do
      def to_xml; ...; end
    end

    using_refine(String) do
      def to_xml; ...; end
    end

    using_refine(Hash) do
      def to_xml; ...; end
    end
  end


>>    IMO, it will be more natural to provide this feature as new
>>    constract with new syntax, instead of Module's methods.
>
> First, I consider it, but I wouldn't like to introduce new keywords.

I thought so, but I think that this feature deserves new
keywords because it is big evolution of Ruby's OO paradigm
(involving semantics change).
However, we should discuss this topic (new keyword) towards
2.0.  Module's methods are not bad, as a part of reflection
features (such as Module#define_method for `def' keyword).


>>  - Is it intended to reject refining module methods?
> It's limitation of the current implementation.

If so, it may be good to raise a NotImplementedError.


> However, I don't think it's critical, because If you'd like to refine
> a module, you can refine a class which includes the module instead.

Do you mean:

  include Math

  $toplevel = self
  module ComplexExt
    def sqrt(x)
      (x >= 0 ? 1 : Complex::I) * super(x.abs)
    end
    refine(class << Math; self; end) { include ComplexExt }
    refine(class << $toplevel; self; end) { include ComplexExt }
  end

  using ComplexExt

  p sqrt(-4)

?

-- 
Yusuke Endoh <[e-mail]>