From: Phlip <phlip2005@...>
Date: 2008-08-24T02:01:00+09:00
Subject: Why 'if 0' succeeds in Ruby

Rubiods:

One of the first "gotchas" here coming from another language is 0 is not like 
'true'. This Daily WTF (which I think someone just posted here) illustrates the 
problem which Ruby solves:

http://thedailywtf.com/Articles/pider-Detection.aspx

"Rather than check the difference between 0 and FALSE (or use a more appropriate 
function), the original developer just dropped the first letter of each crawler 
name so that strpos doesn't return 0."

     $spider_footprint = array('ooglebot', 'rawler', 'pider', 'ulliver',
                               'arvest', 'ahoo! Slurp');
     foreach($spider_footprint as $spider_name)
     {
        if (strpos($agent, $spider_name))
        {
           $is_spider = 1;
...

The problem is not that the programmer did not want to add FALSE != . The 
problem is that language treats 0 as false, when 0 positively means we have a 
good value with a 0 inside it.

0 as FALSE is a legacy of languages that could not distinguish 0 and NULL.

So the Ruby version would work like:

     if agent.index('googlebot')

So, once again, Ruby gives us the right defaults, precedents, and operations 
that do much more, with much less code.

-- 
   Phlip