From: Robert Klemme <shortcutter@...>
Date: 2012-02-23T22:10:28+09:00
Subject: Re: How are closures implemented?

On Mon, Feb 20, 2012 at 11:23 PM, Brian Candler <b.candler@pobox.com> wrote:
> Ralph Shnelvar wrote in post #1047769:
>> How are closures implemented?  How does the closure know about its
>> environment?
>
> The closure *is* the environment.
>
> Are you familiar with local variables allocated on a stack? Then instead
> imagine stack frames allocated out of the heap, in a linked list.
> Instead of being deallocated at the end of a function, they are
> garbage-collected when there are no more references to them, just like
> any other object.

This is the best explanation about closures I have read in a long time, Brian!

Ralph, try this and see whether it helps the explanation sink in:

def f(x)
  [
    lambda { x += 1 },
    lambda { x += 0.5 },
  ]
end

a, b = f(0)

3.times do
  p a.call, b.call
end

Note how there is just a single environment which is shared by the two closures.

Kind regards

robert

-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/