From: dblack@...
Date: 2006-03-14T10:08:49+09:00
Subject: Re: array element access

Hi --

On Tue, 14 Mar 2006, Mike Austin wrote:

> dblack@wobblini.net wrote:
>> Hi --
>> 
>> On Tue, 14 Mar 2006, Mike Austin wrote:
>> 
>>> Tomas Fischer wrote:
>>>> Hi,
>>>> 
>>>> I've got an array a= [1,2,3,4,5,6] and want to access each second 
>>>> element:
>>>> b=[2,4,6]. How is this done in ruby?
>>>> 
>>>> I know, that I can use a for-loob and modulo operator, but I think there 
>>>> is a "ruby way" of doing this.
>>>> 
>>>> Thanks.
>>>> tomas
>>> 
>>> I've always been intrigued by creating a generalized enumeration system. 
>>> Have you guys seen this: http://www.rubyweeklynews.org/20050710 : 
>>> accessing index inside map.  For example:
>>> 
>>> (1..10).collect.with_index { |v, i| v * i }
>>> 
>>> I think that is sweet!  I wonder if it can be generalized enough to do 
>>> this:
>>> 
>>> file.collect.each_byte.with_index { |b, i| b + 1 }
>> 
>> I'm not sure why, but to my eye this has always looked somewhat
>> obscure.  I guess it's something about having to read to the right,
>> even to the extent of not seeing a block, before I know what's being
>> returned (array vs. enumerator).  It's almost as if the call to
>> collect wasn't a "real" call to collect, but rather a kind of
>> place-holder for a collect operation.  I'm not sure.
>
> Ok, what if you rearrange the order of the calls:
>
> file.each_byte.with_index.collect { |b, i| b + 1 }
>
> That's more left-to-right object-oriented sounding.  Come to think of it I 
> like this better because now collect is at the end, and that is the the final 
> intent (with the block being next to it).

There's still something I don't like about using method-chaining
syntax for this.  It may just be a failure of imagination on my part.


David

-- 
David A. Black (dblack@wobblini.net)
Ruby Power and Light, LLC (http://www.rubypowerandlight.com)

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