From: James Edward Gray II <james@...>
Date: 2006-10-13T22:18:43+09:00
Subject: Re: Silent out-of-index problems--how much of a problem are they really?

On Oct 12, 2006, at 11:34 PM, Kenneth McDonald wrote:

> 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.

As has been shown, Array does include a fetch() method that throws  
IndexError.  I would say the fact that Ruby has an entire error type  
just for this case shows that it is not being ignored.

In practice, this just isn't much of an issue in Ruby.  Like off-by- 
one errors, this pretty much just goes away with the pervasive use of  
iterators.

> So my question is, _in practice_, how difficult is it to track down  
> index-out-of-bounds-errors in Ruby?

Well, Rubyists are big fans of Test Driven Development (TDD).  Two of  
the many advantages of TDD are that it causes you to write very small  
methods and isolate the issues of those methods with tightly focused  
tests.  When doing this, it should be fairly rare that you are  
scanning hundreds of line of code for a trivial out of bounds error  
like this.  That's why we like it.  ;)

James Edward Gray II