From: Logan Capaldo <logancapaldo@...>
Date: 2006-08-01T09:50:23+09:00
Subject: Re: I thought this was the one that worked?


On Jul 31, 2006, at 6:48 PM, Chad Perrin wrote:

> On Tue, Aug 01, 2006 at 07:05:31AM +0900, Logan Capaldo wrote:
>>
>> On Jul 31, 2006, at 5:13 PM, Chad Perrin wrote:
>>
>>> On Tue, Aug 01, 2006 at 04:57:48AM +0900, Logan Capaldo wrote:
>>>>
>>>> All these examples are lexical scoping. Ruby doesn't really have
>>>> dynamic scoping although you can sort of abuse instance  
>>>> variables to
>>>> achieve similar effects.
>>>>
>>>> The difference is that blocks are closures, where def, class, and
>>>> module aren't.
>>>
>>> Wait . . . you mean that *all blocks* are automagically lexical
>>> closures, as though declared lexical variables within them have
>>> gone out
>>> of scope?  I imagine I'm probably misunderstanding you, but if not,
>>> that's a pretty nifty bit of trickery.
>>>
>> I'm not sure I understand your question. All blocks (by blocks I mean
>> do / end and { } ) are (lexically scoped) closures.
>
> I'll use a Perl example:
>
> sub foo {
>   my $bar = 1;
>   return sub { print ++$bar };
> }
>
> my $baz = foo();
>
> Voila.  $baz contains a lexical closure.  This is the case because the
> return value from foo() was lexically "closed" by virtue of $bar going
> out of scope, but its value still being accessible via the coderef
> returned from foo() and assigned to $baz.
>

Yes. It is just like perl.

% cat closure.rb
def foo
   bar = 1
   lambda { puts (bar += 1) }
end

baz = foo()

baz.call
baz.call

% ruby closure.rb
-:13: warning: don't put space before argument parentheses
2
3



> -- 
> CCD CopyWrite Chad Perrin [ http://ccd.apotheon.org ]
> "The measure on a man's real character is what he would do
> if he knew he would never be found out." - Thomas McCauley
>