From: Csaba Henk <csaba@..._for_avoiding_spam.org>
Date: 2005-01-29T08:50:53+09:00
Subject: Proc rebinding

In ruby there is such a thing as rebinding a proc object, as the example
below shows:

#####
class Foo
  def initialize
    @name = "anna"
  end
  @@hello = proc{ puts "hello #{@name}" }
  define_method :hello, @@hello
end

f=Foo.new
f.hello
class Foo; @@hello[]; end
####

When you run the above, it writes:

hello anna
hello

A Proc obejct carries its binding with itself (ie. is a closure), as it
is well known. When @@hello was created, it did not know any @name. But
then it was passed to define_method, and the resulting method "hello"
can find @name in the instances. That is, ruby altered the bindings of
(some kind of copy of) @@hello, and only after that has it been attached
as a method. (Or rather, the binding is altered upon instantiation?)

But all of this happened under the hood.

What do you think of an explicit way of altering method bindings? I ask
it because I could have made good use of that now (I tell the concrete
example, is someone is interested). When one works with a bunch of
anonymous processes, it's not handy/feasible to make them methods just
for getting the binding changed.

* Would it be useful?
* A few lines of C which does it?
* Is it possible with EvilRuby?
* Is something like this planned (has it been discussed)?

Csaba