From: Ross Bamford <rosco@...>
Date: 2006-01-04T06:22:58+09:00
Subject: Re: Implicit block parameter?

On Tue, 03 Jan 2006 18:39:48 -0000, <dblack@wobblini.net> wrote:

> Hi --
>
> On Wed, 4 Jan 2006, Ross Bamford wrote:
>
>> 	[[1,2,3],[2,3,4],[3,4,5]].each { it.select { it % 2 == 0 } }
>>
>> (I've not tested that btw but you get the idea). However I guess with  
>> that it's also potentially confusing when using the implicit idea,  
>> since it has the same magic variable meaning two different things in  
>> the same line. I guess in this case I'd probably declare the argument  
>> in the select block anyway (as 'i' or something).
>
> That's actually another good argument against "it": you'd be trampling
> the outer it with the inner it.  And having to remember to declare the
> inner argument to protect it from this really puts the whole thing in
> the "added to the language as an afterthought" category.
>

Hmm, I know. As I was writing it I started thinking about that and all the  
other little subtleties it could create. Generally I'm never happy with a  
solution that requires me to do more thinking :D. Based on the C-side  
patch that was posted by Dominik Bathon the inner/outer it thing does  
actually work, but isn't ideal from a readability perspective I guess.

(As an aside, with that patch the approach I suggested *doesn't* work,  
since it doesn't check whether 'it' is already declared so tramples the  
outer it even if you declare a block argument on the inner).

I'm not sure I understand the afterthought thing, though - wouldn't any  
suggested enhancement that happened to be implemented now be an  
afterthought? But anyhow this has snowballed a bit - originally I really  
wanted a way to do it from the Ruby side, and more for fun than profit.  
I've not been here long enough to start suggesting changes in Ruby itself  
but I just wondered if it'd been considered before...

Cheers,

-- 
Ross Bamford - rosco@roscopeco.remove.co.uk