From: Dave Thomas <Dave@...>
Date: 2000-09-02T08:01:51+09:00
Subject: [ruby-talk:4736] Re: Possible regex bug?

hal9000@hypermetrics.com writes:

> OK, I'm trying to match an optional comma followed by
> one or more spaces...
> 
> The sample program regx.rb leads me to believe that
> this will work: /,? */

Always be careful with patterns containing '*'. For example,

   'caaaaaat'  =~ /a*/    # => 0
   p $&                   # => ""

/a*/ matched the string by matching exactly _zero_ 'a's at the start.

> But: p "4.2, 3.1, 5.3".split(/,? */)

Your pattern also matches a zero length string: 'no commas and no
spaces'. This is why split isn't doing what you want.

However, in your problem definition, you said you wanted an optional
comma followed by _one_ or more spaces. That's a different beast:

   "4.2, 3.1, 5.3".split(/,? +/) # => ["4.2", "3.1", "5.3"]

                             ^
     one or more... ---------+

You could also have used scan:

   "4.2, 3.1, 5.3".scan(/[\d.]+/) # => ["4.2", "3.1", "5.3"]


Regards


Dave