From: "David A. Black" <dblack@...>
Date: 2005-04-22T21:17:50+09:00
Subject: Re: for .. in .. else?

Hi --

On Fri, 22 Apr 2005, Adam Keys wrote:

> On Apr 21, 2005, at 5:46 PM, Hal Fulton wrote:
>> FWIW I'll offer this (untested) alternative:
>> 
>>  <table>
>>    <tr><th>Songs</th></tr>
>>    <% unless song_list.each do |song|%>
>>      <tr><td><%= song.name %></td></tr>
>>      <% end.empty? %>
>>      <tr><td>no songs!</td></tr>
>>    <% end %>
>>    </tr>
>>  </table>
>
> A few weeks ago I was on a crusade to not create temporary Arrays and Hashes. 
> I wrote a bit of code something like this:
>
> ary.reject do |item|
>  item.some_predicate?
> end.each do |doodad|
>  doodad.do_something
> end
>
> I was showing it to a non-Rubyist and he thought it was a little hard to 
> read.  I agreed it may be a little too clever for its own good.  Obviously 
> Hal doesn't think so :).  Does anyone else have strong feelings on code like 
> the above?

Yours is different from Hal's, because in Hal's the iteration through
the song list is sort of a side-effect of the testing of the
condition, whereas you're just doing a standard chaining thing.  And
you do create a temporary array :-)  (the return value of #reject)

You could perhaps make it easier to read with a different formatting:

   ary.reject {|e| e.some_predicate? } .each do |f|
     f.do_something
   end

or something.  (Definitely lose the one-space indenting.)  If your
friend still has trouble with it, buy him the Pickaxe :-)


David

-- 
David A. Black
dblack@wobblini.net