From: Austin Ziegler <halostatue@...>
Date: 2005-10-19T12:26:08+09:00
Subject: Re: Anonymous methods, blocks etc. (Cont. 'default block params')

On 10/18/05, Trans <transfire@gmail.com> wrote:
> Austin Ziegler wrote:
>> On 10/18/05, Sean O'Halpin <sean.ohalpin@gmail.com> wrote:
>>> On 10/18/05, Eric Mahurin <eric_mahurin@yahoo.com> wrote:
>>>> But, I kind of still wish we had a syntax where the variables in a
>>>> block/lambda were local (non-closure) by default.
>>> Maybe if we say it often enough? ;)
>> Doubtful. I think to convince matz, real examples would need to be
>> presented (as an RCR!) as to why this is necessary. IANM, but IMO
>> theoretical need and wish ain't sufficient.
> The easist is the old gotcha. Programmer has code (doesn't much matter
> what it is)

[...]

> And wants to resue the lambda so uses old fashion copy and paste:
>
>   class Y
>     def bar( n )
>       x = n * 3
>       l = lambda { |a| x = a**2; x + 1 }
>       return x + l[3]
>     end
>   end
>
> Oopsy.

Dumb programmer. This part isn't nearly sufficient to justify a new
scope or kind of lambda (lambda without closure), IMO. If you want to
reuse a lambda that you're not passing around, make it a method.

> For something a little more concrete:

[...]

> Now try:
>
>   class X
>     def x;1;end
>   end
>   => nil
>
>   Y = Class.new(X) do
>     X = Class.new do
>       def x;2;end
>     end
>     def x;3;end
>   end
> (irb):5: warning: already initialized constant X
>   => Y
>
>   X.new.x
>   => 2
>   Y.new.x
>   => 3
>   Y::X.new.x
>   (irb):12: warning: toplevel constant X referenced by Y::X
>   => 2

This isn't a closure problem. This is a constant lookup problem, and
Matz has said that this should be fixed moving forward.

As I said, I'm very skeptical.

-austin
--
Austin Ziegler * halostatue@gmail.com
               * Alternate: austin@halostatue.ca