From: brk@...
Date: 2001-03-07T16:07:23+09:00
Subject: [ruby-talk:12214] Re: FEATURE REQUEST: 'my' local variables

If you want to use this sort of idiom, try this example which doesn't
require any changes to the language:

require 'context' #See below...
x = 0
{
  my = Context.new
  my.x = 7
  my.x #-> 7
}
x #-> 0

Here's the code for Context (suggestions welcome, I'm sure there are better
ways to do this). You can probably use something like this to suit your
needs. Also, if you want immutable names, do this:

my = Context.new(false)
my.x = 2
my.x # -> 2
my.x = 5 #-> RuntimeError: Can't reassign variable

#context.rb
class Context
  @@method_template = %q{
    def X
      @names['X']
    end
    if @mutable then
      def X=(val)
        @names['X'] = val
      end
    else
      def X=(val)
        raise RuntimeError, "Can't reassign variable"
      end
    end
  }
  
  def initialize(mutable = true)
    @names = Hash.new
    @mutable = mutable
  end
  
  def method_missing(sym, *args)
    attrib = sym.to_s
    if attrib[-1,1] != "="
      raise NameError, "undefined method '#{attrib}' for object #{to_s}" 
    end
    prop_name = attrib[0, (attrib.length - 1)]
    new_meth_def = @@method_template.gsub(/X/, prop_name)
    instance_eval(new_meth_def)
    @names[prop_name] = args[0]
  end	
end	


Hope that helps,

Bryn



-----Original Message-----
From: cjon@sapphire.engin.umich.edu
[mailto:cjon@sapphire.engin.umich.edu]
Sent: Tuesday, March 06, 2001 9:10 PM
To: ruby-talk@ruby-lang.org; ruby-talk@netlab.co.jp
Subject: [ruby-talk:12207] Re: FEATURE REQUEST: 'my' local variables


Leo Razoumov (see_signature@127.0.0.1) wrote:
> # PROPOSED FEATURE:
> x = 0  #line_1
> {
>   my x = 7  # new varible 'x' shadowing 'x' from line_1 
>   x  # -> 7
> }
> x    # -> 0

This seems to me like it would be very useful.

Cullen J O'Neill
--
cjon@engin.umich.edu