From: Daniel Waite <rabbitblue@...>
Date: 2007-09-28T01:31:18+09:00
Subject: Re: Break apart a string by kind of characters

Daniel Waite wrote:
> Hi all, I've an interesting problem. Imagine the following string:
> 
> 'a1000aa'
> 
> I want to break it apart like so:
> 
> [ 'a', '1000', 'aa' ]
> 
> I did a search on the forums and came up with this regex:
> 
> 'a1000aa'.scan(/((.)\2*)/).map { |i| i[0] }
> 
> Which is pretty close, but it groups on a change of character, so I
> would get:
> 
> [ 'a', '1', '000', 'aa' ]
> 
> I tried playing around with the regex (e.g. swapping the . for (\d|\w))
> but to no avail.
> 
> Any ideas?

I figured out one possible solution. Granted, it's not as elegant as a 
single regex, but it works and I understand it. Here goes...

First, I opened up class String to add some convenience and make things 
a bit shorter:

class String

  def letter?
    self.first.scan(/[A-Za-z]/).empty? ? false : true
  end

  def digit?
    self.first.scan(/[0123456789]/).empty? ? false : true
  end

end

Any my method:

def break_apart_rule_increment
  groups = Array.new
  string = 'a1000aa'

  string.each_char do |character|
    # Put the first character into a group.
    groups << character and next if groups.empty?

    # If this character is of the same kind as the last,
    # add it to the group, otherwise, create a new group
    # and put it there.
    if (groups.last.letter? and character.letter?) or 
(groups.last.digit? and character.digit?)
      groups.last << character
    else
      groups << character
    end
  end

  groups
end

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