From: Laurent Sansonetti <laurent.sansonetti@...>
Date: 2012-12-03T05:40:47+09:00
Subject: [ruby-core:50487] Re: [ruby-trunk - Feature #4085] Refinements and nested methods

Hi guys,

Sorry to hijack the conversation, but I have been quickly reading the
thread and wow, it sounds like the specifications for this feature
changed at least a couple times. I was wondering if the core team
(Matz?) has been working on a readable spec that could be shared with
language implementors? Such a spec would be helpful (at least to me)
to understand the behaviors and how to implement them. I'm looking at
adding the 2.0 stuff in RubyMotion.

Sounds like RubySpec could be used for that?

Also, for what it counts, I have to agree with Charles that this
feature seems to be very ambitious for 2.0.

Regards.
Laurent

On Sun, Dec 2, 2012 at 7:02 AM, headius (Charles Nutter)
<headius@headius.com> wrote:
>
> Issue #4085 has been updated by headius (Charles Nutter).
>
>
> headius (Charles Nutter) wrote:
>> If there's a using Christmas::Refinements appears somewhere above this code, things are different. *Both* to_s calls will see the refined to_s (ANSI.blink version). Since that version does not super, both to_s's would blink, but neither would be red (since neither the original to_s nor RedString#to_s get called).
>
> I should note that this is based on what I *think* matz and shugo envision for refinements today. This could certainly change in the future (or I could be wrong about what they envision).
> ----------------------------------------
> Feature #4085: Refinements and nested methods
> https://bugs.ruby-lang.org/issues/4085#change-34308
>
> Author: shugo (Shugo Maeda)
> Status: Assigned
> Priority: Normal
> Assignee: matz (Yukihiro Matsumoto)
> Category: core
> Target version: 2.0.0
>
>
> =begin
>  As I said at RubyConf 2010, I'd like to propose a new features called
>  "Refinements."
>
>  Refinements are similar to Classboxes.  However, Refinements doesn't
>  support local rebinding as mentioned later.  In this sense,
>  Refinements might be more similar to selector namespaces, but I'm not
>  sure because I have never seen any implementation of selector
>  namespaces.
>
>  In Refinements, a Ruby module is used as a namespace (or classbox) for
>  class extensions.  Such class extensions are called refinements.  For
>  example, the following module refines Fixnum.
>
>    module MathN
>      refine Fixnum do
>        def /(other) quo(other) end
>      end
>    end
>
>  Module#refine(klass) takes one argument, which is a class to be
>  extended.  Module#refine also takes a block, where additional or
>  overriding methods of klass can be defined.  In this example, MathN
>  refines Fixnum so that 1 / 2 returns a rational number (1/2) instead
>  of an integer 0.
>
>  This refinement can be enabled by the method using.
>
>    class Foo
>      using MathN
>
>      def foo
>        p 1 / 2
>      end
>    end
>
>    f = Foo.new
>    f.foo #=> (1/2)
>    p 1 / 2
>
>  In this example, the refinement in MathN is enabled in the definition
>  of Foo.  The effective scope of the refinement is the innermost class,
>  module, or method where using is called; however the refinement is not
>  enabled before the call of using.  If there is no such class, module,
>  or method, then the effective scope is the file where using is called.
>  Note that refinements are pseudo-lexically scoped.  For example,
>  foo.baz prints not "FooExt#bar" but "Foo#bar" in the following code:
>
>    class Foo
>      def bar
>        puts "Foo#bar"
>      end
>
>      def baz
>        bar
>      end
>    end
>
>    module FooExt
>      refine Foo do
>        def bar
>          puts "FooExt#bar"
>        end
>      end
>    end
>
>    module Quux
>      using FooExt
>
>      foo = Foo.new
>      foo.bar  # => FooExt#bar
>      foo.baz  # => Foo#bar
>    end
>
>  Refinements are also enabled in reopened definitions of classes using
>  refinements and definitions of their subclasses, so they are
>  *pseudo*-lexically scoped.
>
>    class Foo
>      using MathN
>    end
>
>    class Foo
>      # MathN is enabled in a reopened definition.
>      p 1 / 2  #=> (1/2)
>    end
>
>    class Bar < Foo
>      # MathN is enabled in a subclass definition.
>      p 1 / 2  #=> (1/2)
>    end
>
>  If a module or class is using refinements, they are enabled in
>  module_eval, class_eval, and instance_eval if the receiver is the
>  class or module, or an instance of the class.
>
>    module A
>      using MathN
>    end
>    class B
>      using MathN
>    end
>    MathN.module_eval do
>      p 1 / 2  #=> (1/2)
>    end
>    A.module_eval do
>      p 1 / 2  #=> (1/2)
>    end
>    B.class_eval do
>      p 1 / 2  #=> (1/2)
>    end
>    B.new.instance_eval do
>      p 1 / 2  #=> (1/2)
>    end
>
>  Besides refinements, I'd like to propose new behavior of nested methods.
>  Currently, the scope of a nested method is not closed in the outer method.
>
>    def foo
>      def bar
>        puts "bar"
>      end
>      bar
>    end
>    foo  #=> bar
>    bar  #=> bar
>
>  In Ruby, there are no functions, but only methods.  So there are no
>  right places where nested methods are defined.  However, if
>  refinements are introduced, a refinement enabled only in the outer
>  method would be the right place.  For example, the above code is
>  almost equivalent to the following code:
>
>    def foo
>      klass = self.class
>      m = Module.new {
>        refine klass do
>          def bar
>            puts "bar"
>          end
>        end
>      }
>      using m
>      bar
>    end
>    foo  #=> bar
>    bar  #=> NoMethodError
>
>  The attached patch is based on SVN trunk r29837.
> =end
>
>
>
> --
> http://bugs.ruby-lang.org/
>