From: Ross Bamford <rosco@...>
Date: 2006-01-04T03:22:58+09:00
Subject: Re: Implicit block parameter?

On Tue, 03 Jan 2006 17:26:15 -0000, <dblack@wobblini.net> wrote:

>>
>> Hmm, I might put together a bit of a proposal and do that. I hope  
>> you'll comment when you vote no, I'd be interested in your perspective  
>> on this :)
>
> I don't like it.  I've never felt there was a problem to solve in this
> area, since it's so easy to specify an argument list.  Having a magic
> variable ("it" or $_ or whatever) seems like a step backwards, in
> terms of clarity and consistency.
>

I do agree that from a readability point of view it's potentially  
confusing, and newcomers to Ruby could look at it and wonder where the  
hell 'it' came from. I think though that $_ is a different argument  
(again, no pun intended), since that introduces stuff like:

	[1,2,3].each { print if ~/.../ }

which I couldn't convincingly argue for even were I paid to do so. This  
kind of 'invisible data' confuses the hell out of me, and is IMHO one of  
Perl's most evil features. On the other hand:

	[1,2,3].each { puts it if it =~ /.../ }

(again ignoring the TMTOWTDI aspect for the sake of example) at least (to  
me) implies some relationship between the message sent and the data - it  
says to me "take each number from the array and output it if it matches  
this". Granted, it's not vastly different from:

	[1,2,3].each { |it| puts it if it =~ /.../ }

but the extra 'it' (or whatever) in there just grates (admittedly only  
slightly) on my nerves. It also gets a bit worse when you have stuff like:

	[[1,2,3],[2,3,4],[3,4,5]].each { |it| it.select { |it| it % 2 == 0 } }
	[[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).

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