From: Peter Zotov <whitequark@...>
Date: 2012-02-20T20:12:22+09:00
Subject: Re: How are closures implemented?

Ralph Shnelvar писал 20.02.2012 12:37:
> I'm one of those people who needs to see/understand a typical
> implementation of something before I can grok how it works.
>
> How are closures implemented?  How does the closure know about its
> environment? Since a block can use the various flavors of eval, it
> seems to me that the closure needs access to everything.

I would just say that for cases like this:

     def a(x); eval("x"); end

Ruby keeps a list of local variables and its names in runtime and has
an internal method_missing dispatch logic which looks up undefined 
methods
in the local variable table.

I wasn't able to find the relevant source in reasonable time, but the
truth is out there. Someone more familiar with MRI sources than me 
could
correct this.

>
> Seems like magic to me.

... and it pretty much _is_ magic.

>
> I have looked at
> http://samdanielson.com/2007/9/6/an-introduction-to-closures-in-ruby
> but I am still not grokking it.
>
> Anyone have a link they can recommend on how closures are 
> implemented?
>
> "Any sufficiently advanced technology is indistinguishable from
> magic." Arthur C. Clarke

-- 
   WBR, Peter Zotov.