From: Glenn Ritz <glenn_ritz@...>
Date: 2010-02-19T23:07:28+09:00
Subject: Re: Adding self to Enumerable

Robert Klemme wrote:
> On 02/18/2010 10:39 PM, Glenn Ritz wrote:
>>>
>>> %w(cat dog mouse).each { |e| s = self; puts "self: #{s.inspect}, e: 
>>> #{e}" }
>>>
>>> or better:
>>>
>>> %w(cat dog mouse).each { |e| puts "self: #{self.inspect}, e: #{e}" }
>> 
>> 
>> I want to be able to refer to the array receiver inside of the block. 
> 
> What is the point of that?  I mean, you can *always* have a reference to
> the instance around.
> 
> s = %w(cat dog mouse)
> s.each {|e| ...}
> 
> Or, in 1.9
> 
> %w(cat dog mouse).tap {|s| s.each {|e| ...}}
> 
> Even if you pass around a block for later usage with #each you can make
> sure the collection is accessible inside the block.
> 
> What is the real use case of this?  Passing the collection into the
> block during iteration feels wrong.  For example, typically when
> iterating modifications of the underlying collection are dangerous.  Why
> do you need this feature?
> 
> Kind regards
> 
>   robert

Sometimes in statistics it's good to be able to access the previous 
element in a collection, not just the current one like in Ruby's each 
method.  So I was thinking that it would be good if I could refer to the 
array itself within the block.  I realize now that there are probably 
better ways to do this. :-)

Also, I find the with_index method on Enumerable objects interesting and 
was trying to figure out a way to write a similar method.  So I asked 
the question just to learn more on what I think is an interesting 
feature of the language.

Thanks,

Glenn
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