From: Logan Capaldo <logancapaldo@...>
Date: 2006-08-01T21:12:18+09:00
Subject: Re: I thought this was the one that worked?


On Aug 1, 2006, at 6:39 AM, Chad Perrin wrote:

> On Tue, Aug 01, 2006 at 06:50:09PM +0900, Just Another Victim of  
> the Ambient Morality wrote:
>>
>>     This seriously sounds like an "if a tree falls in the forest,  
>> does it
>> make a sound?" kind of situation.  In other words, it's a semantic
>> argument...
>
> Okay, let's translate that question into the terms we're actually
> discussing.
>
>   1. If a tree falls in the forest, and there's no one around to hear
>   it, does it still make a sound?
>
>   2. If a lambda has the ability to access its context, but there  
> isn't
>   any context to access, is it still a closure?
>
>
>>
>>     Personally, I would call them closures, if they have access to  
>> their
>> environments.
>>     Perhaps we can agree to call a closure a block of code that  
>> has the
>> _ability_ to access variables of their enclosing scope, rather  
>> than strictly
>> requiring that they take advantage of this ability?
>
> Not yet.  See above, re: blocks falling in a forest.
>
> I'm beginning to think the question of whether it's actually a closure
> really IS a question for a programming koan, after all.  If so, I'm  
> glad
> we've at least narrowed the discussion down to this point at last.
>
> It'd be pretty neat to be responsible for the creation of a new
> programming koan, anyway.  I'm going to go add this to my sig rotation
> right now.
>
> -- 
> CCD CopyWrite Chad Perrin [ http://ccd.apotheon.org ]
> This sig for rent:  a Signify v1.14 production from http:// 
> www.debian.org/
>


More examples to chew on:

class A
   def make_closurish_thing
     lambda { puts "Hello" }
   end
end


a = A.new
c = a.make_closurish_thing
c.call
def a.puts(*args)
   super("Access of enclosing scope")
   super
end
c.call


class B
   def close_me
     x = 1
     lambda{|x| eval(x) }
   end
end

b = B.new
c = b.close_me

c.call("puts 'Am I a closure?'")
c.call("puts 'How about now?'; puts x")