From: Mike Cargal <mike@...>
Date: 2010-11-04T20:46:26+09:00
Subject: Re: Regular Expression

regex = /^(A(?!A)|B(?!B)|C(?!C)|D{1,2}(?!D))+$/

["ABCDD","CA","CAD","CADD","CADDD","DAD","BAC","BBAD","AABCCD"].each do |string| 
   puts "'#{string}' => #{string.match(regex)}"
end

==============
'ABCDD' => ABCDD
'CA' => CA
'CAD' => CAD
'CADD' => CADD
'CADDD' => 
'DAD' => DAD
'BAC' => BAC
'BBAD' => 
'AABCCD' => 
==============
On Nov 2, 2010, at 5:55 PM, Kendall Gifford wrote:

> On Tue, Nov 2, 2010 at 3:34 PM, Richard Conroy <richard.conroy@gmail.com> wrote:
>> On Tue, Nov 2, 2010 at 9:05 PM, Dv Dasari <dv.mymail@gmail.com> wrote:
>> 
>>> I am trying to write a reqular expression to match a word with my input
>>> string.
>>> 
>>> Input string can be ( inpstr = ABCDD )
>>> 
>>> Any suggestion on how I can fix this?
>>> 
>> 
>> You are going to need some more advanced regexes to get a match in the way
>> you are hoping for.
>> 
>> I would get out a copy of a good regex cheat sheet, and work through some
>> examples in http://rubular.com
>> http://www.addedbytes.com/download/regular-expressions-cheat-sheet-v2/pdf/
>> 
>> The main reason for rubular is that you list all of the regexes you want to
>> match, and which to reject, and keep tweaking until you get what you want.
>> 
>> OTOH this regex might scratch your itch:
>> /^A?B?C?D{0,2}$/
>> 
> 
> The above works so long as each of ABC or D must come in said order,
> if present. This goes against the OP's examples: CA, DAD, and BAC.
> 
> My suspicion is that you're problem isn't solvable by a regular
> expression alone, but that you'll need to do some parsing (still
> possibly using regular expressions in the process).
> 
> -- 
> Kendall Gifford
> zettabyte@gmail.com
> 

Mike Cargal

mike@cargal.net
http://blog.mikecargal.com