From: Nicholas Van Weerdenburg <vanweerd@...>
Date: 2005-01-21T03:53:13+09:00
Subject: Re: Confused about variable "declarations"

On Fri, 21 Jan 2005 03:01:02 +0900, Ilmari Heikkinen <kig@misfiring.net> wrote:
> 
> On 20.1.2005, at 19:31, Robert Klemme wrote:
> 
> >
> > "Mark Hubbart" <discordantus@gmail.com> schrieb im Newsbeitrag
> > news:de63abca050120090877cc9971@mail.gmail.com...
> >> On Thu, 20 Jan 2005 21:01:01 +0900, Graham Nicholls
> >> <graham@rockcons.co.uk> wrote:
> >>> No worries, and thanks, but I think that the problem was that offset
> > is
> >>> being set inside an iterator (they still confuse me - any pointers to
> > a
> >>> good explanation would be nice!), which means that it is out of scope
> >>> outside the iterator.
> >>
> >> A short explanation: Blocks have a sort of "leaky scope", where
> >> variables from outside the scope can leak in and out, but those that
> >> are from the inside don't leak out. for example:
> >
> > While I completely agree with your explanation the word "leaky"
> > strikes me
> > as odd as it seems to suggest  uncommon or defective behavior: it's
> > very
> > common in programming languages, that variables are visible in nested
> > scopes but not surrounding scopes:
> >
> 
> This may be the leaky case:
> 
> x = 10
> arr = (x..100).map{|x| x*2}
> x #=> 100
> 
> :)
> 
> --
> Ilmari Heikkinen
> 
> 

I'm quite fond of this behaviour. It works nicely in the "optparse" library.

e.g.
require "optparse"
logfile=nil;
opts=OptionParser.new do |opt|
    opt.on('--logfile', '-l', "Specify log file"){|logfile|}
end

But I was confused initially since I was thinking in C/Java scope
terms at first, and then Perl terms at second. But now I'm happy. I do
suppose it might be nice to allow seeping (fuzzing didn't sound write)
out. That would save some typing, without too much confusion.

Nick
-- 
Nicholas Van Weerdenburg