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Feature #4085

Refinements and nested methods

Added by shugo (Shugo Maeda) over 9 years ago. Updated over 7 years ago.

Status:
Closed
Priority:
Normal
Target version:
[ruby-core:33322]

Description

=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


Files

refinement-r29837-20101124.diff (70.3 KB) refinement-r29837-20101124.diff shugo (Shugo Maeda), 11/24/2010 10:12 PM
control_frame_change-r29944-20101127.diff (31.5 KB) control_frame_change-r29944-20101127.diff a patch to add klass to rb_control_frame_t shugo (Shugo Maeda), 11/27/2010 01:39 PM
refinements-r29944-20101127.diff (33.8 KB) refinements-r29944-20101127.diff a patch to support Refinements shugo (Shugo Maeda), 11/27/2010 01:39 PM
nested_methods-r29944-20101127.diff (8.65 KB) nested_methods-r29944-20101127.diff a patch to change behavior of nested methods shugo (Shugo Maeda), 11/27/2010 01:39 PM

Related issues

Related to Ruby master - Bug #7271: Refinement doesn't seem lexicalClosedshugo (Shugo Maeda)11/04/2012Actions
Related to Ruby master - Feature #7251: using usings in usinged ModuleClosedshugo (Shugo Maeda)10/31/2012Actions
Has duplicate Ruby master - Feature #6287: nested method should only be visible by nesting/enclosing methodClosedmatz (Yukihiro Matsumoto)04/13/2012Actions

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