From: Kenneth McDonald <kenneth.m.mcdonald@...>
Date: 2006-10-13T13:34:33+09:00
Subject: Silent out-of-index problems--how much of a problem are they really?

As a Python user starting to mess around with Ruby, one of my biggest 
concerns is the fact that so many operations on lists 'fail silently' 
(return nil) when given list indices that are out of bounds. In 
particular, I worry that this might produce hard-to-track down errors, 
as the problem might not show up until one tries to do something with 
the returned value(s); and by that may be somewhere far away in the 
code. Certainly the guilty list access won't show up in the call stack.

On the other hand, it's often thought that dynamic languages will result 
in lots of difficult-to-find problems due to the lack of strong typing, 
but both Python and Ruby users know that's not the case.

So my question is, _in practice_, how difficult is it to track down 
index-out-of-bounds-errors in Ruby? It can certainly be a godawful 
problem in C, and I'm pretty sure it would be in Python, too, if 
exceptions weren't thrown. And in Ruby, how does one track done where 
such errors actually occur? In Python, I can simply look at the stack trace.

This isn't a criticism of Ruby. (Well, one aspect maybe). I'm looking at 
Ruby because there are a lot of things (documentation tools, 
consistency, gems, others) that it does better than Python. But I do 
worry about silent index errors.

Thanks,
Ken