From: Joel VanderWerf <vjoel@...>
Date: 2005-08-25T09:28:03+09:00
Subject: Re: regexp character classes and +

Mark Volkmann wrote:
> On page 71 of Pickaxe 2, discussing character classes, it says "The
> significance of special regular expression characters (including +) is
> turned off inside the brackets."
> 
> Why is this a valid regular expression (+ not the first character in
> the character class)
> 
> %r{^[-+*/]$}
> 
> but this isn't? (+ is the first character in the character class)
> 
> %r{^[+-*/]$}
> 

The - character denotes a range in a regexp.

irb(main):001:0> "abc" =~ /[a-c]{3,3}/
=> 0

Putting - at the beginning of the bracket expression makes it literal.

-- 
      vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407