From: Robert Klemme <shortcutter@...>
Date: 2007-10-27T01:55:01+09:00
Subject: Re: Skip the first invocation e.g. skip_first { foo }

On 26.10.2007 17:50, mortee wrote:
> Robert Klemme wrote:
>> 2007/10/26, mortee <mortee.lists@kavemalna.hu>:
>>> The bad news is that I guess from inside the block passed to the
>>> iterator, you have no way (at least no nice way) to keep track of the
>>> iteration count, and make decisions based on it. You either have to call
>>> each_with_index, and make use of the passed index, but this won't work
>>> with other iterators.
>> It does, if you use Enumerator:
>>
>> 17:26:33 ~$ irb -r enumerator
>> irb(main):001:0> %w{foo bar baz}.to_enum(:each_with_index).
>> irb(main):002:0* map {|e,i| i % 2 == 0 ? e : :empty}
>> => ["foo", :empty, "baz"]
>> irb(main):003:0>
> 
> Thanks, this is nice - I haven't known it existed. However,
> unfortunately it's less "elegant" than simply using the iterator itself,
> and enclosing parts of the loop body in skip_first{...}

Obviously tastes differ. :-)  Personally I find the effort you have to 
invest to get a correct working and failure safe version of skip_first 
extremely inelegant for a problem which has a much simpler solution.

Kind regards

	robert