From: dblack@...
Date: 2006-09-25T02:03:14+09:00
Subject: Re: Use of array shift and blocks

Hi --

On Mon, 25 Sep 2006, Toby Rodwell wrote:

> unknown wrote:
>> ...
>> shift doesn't take a block.  You can write one but shift won't call
>> it.
>>
>> You could do this:
>>
>>    until array.empty?
>>      puts array.shift
>>    end
>>
>>
>> David
>
> Many thanks David.  I'm not sure I understand why shift doesn't take a
> block, but thanks for confirming it.

I expect it's because shifting is a (conceptually) atomic operation.
If you need to examine what got shifted, you can get the return value.
If you need to examine the newly-shortened array, you can examine it
directly.  There's really nothing for a block to do.

Consider, by way of contrast, something like String#sub, where you
find something and replace it with something -- and you might want to
have a handle on the 'something', in the middle, so that you can
manipulate it to generate the eventual replacement string.


David

-- 
                   David A. Black | dblack@wobblini.net
Author of "Ruby for Rails"   [1] | Ruby/Rails training & consultancy [3]
DABlog (DAB's Weblog)        [2] | Co-director, Ruby Central, Inc.   [4]
[1] http://www.manning.com/black | [3] http://www.rubypowerandlight.com
[2] http://dablog.rubypal.com    | [4] http://www.rubycentral.org