From: Brad Phelan <phelan@...>
Date: 2007-08-13T19:20:00+09:00
Subject: Re: Split a string based on change of character

Andrew Savige wrote:
> For a string "ZBBBCZZ", I want to produce a list ["Z", "BBB", "C", "ZZ"]
> That is, break the string into pieces based on change of character.
> 
> Though this works:
> 
>   s = "ZBBBCZZ"
>   x = s.scan(/((.)\2*)/).map {|i| i[0]}

Another variant which gets rid of one of the capture
groups and does introduce an artificial split character

Enumerator.new(s, :scan, /(.)\1*/).map {$&}

Note the $& will not work in the example

 >   x = s.scan(/((.)\2*)/).map {|i| i[0]}

because the map is run on an array after the
scan has happened. To run the map inline with
the scan you need the Enumerator object.

I doubt using Enumerator is any faster though.

Wouldn't it be nicer if scan returned an
enumerable instead of an array. We could
define

class String
    def scan_enum regexp
	Enumerator.new self, :scan, regexp
    end
end

and then be able to do

s.scan_enum(/(.)\1*/).map {$&}

--
Brad Phelan
http://xtargets.com