From: Shugo Maeda <shugo@...>
Date: 2009-07-24T01:00:02+09:00
Subject: [ruby-core:24533] Re: lvar_propagate

Hi,

2009/7/19 Shugo Maeda <shugo@ruby-lang.org>:
> I created a patch on Friday:
>
> �http://shugo.net/RubyKaigi/2009/no-implicit-lexical-scope.diff

The presentation slides are available at:

  http://shugo.net/RubyKaigi/2009/slide.pdf

I'm not serious about magic comment.  It's just a hack for the presentation.

However, I prefer flat local variable scope rather than local variable
propagation.
Local variable propagation looks too complex because there is no
lexical difference between a local variable reference and an
invocation of the method which name is same to the local variable.  It
may be more implicit than the current behavior.

> I will talk about it in RubyKaigi2009 from 16:00 today. �In that talk,
> I will propose another feature to specify explicit scope. �It is
> implemented by just 6 lines in C.

I proposed Kernel#let.

    x, y = 0, 1
    let {|x, y = 2|
      x = 3
      p y   #=> 2
    }
    p x     #=> 0
    p y     #=> 1

Thanks to the changes of block parameters in Ruby 1.9, you can specify
the initial value of them.  It looks like Lisp, doesn't it?

-- 
Shugo Maeda