From: Mike Cargal <mike@...>
Date: 2010-11-05T08:40:04+09:00
Subject: Re: Regular Expression

double grrrrr..... (I messed up the parentheses on the last last one)

regex = /^(A(?!.*A)|B(?!.*B)|C(?!.*C)|D(?!.*D.*D)|DD(?!.*D))+$/

["ABCDD","CA","CAD",
 "CADD","CADDD","DAD","DADD","DADAD","ADD",
 "BAC","BBAD","AABCCD",
 "DADD","DADBD","ABCDDA",
 "MIKE"].each do |string|    
  puts "'#{string}' => #{string.match(regex)}"
end
On Nov 4, 2010, at 7:14 PM, Mike Cargal wrote:

> grrr......
> 
> regex = /^(A(?!.*A)|B(?!.*B)|C(?!.*C)|D(?!.*D.*D|DD(?!.*D)))+$/
> 
> ["ABCDD","CA","CAD",
>  "CADD","CADDD","DAD","DADD","DADAD","ADD",
>  "BAC","BBAD","AABCCD",
>  "DADD","DADBD","ABCDDA",
>  "MIKE"].each do |string|    
>   puts "'#{string}' => #{string.match(regex)}"
> end
> 
> ======================
> 'ABCDD' => ABCDD
> 'CA' => CA
> 'CAD' => CAD
> 'CADD' => CADD
> 'CADDD' => 
> 'DAD' => DAD
> 'DADD' => 
> 'DADAD' => 
> 'ADD' => ADD
> 'BAC' => BAC
> 'BBAD' => 
> 'AABCCD' => 
> 'DADD' => 
> 'DADBD' => 
> 'ABCDDA' => 
> 'MIKE' => 
> ======================
> On Nov 4, 2010, at 7:06 PM, Kendall Gifford wrote:
> 
>> On Thu, Nov 4, 2010 at 4:53 PM, Mike Cargal <mike@cargal.net> wrote:
>>> 
>>> On Nov 4, 2010, at 1:34 PM, Kendall Gifford wrote:
>>> 
>>>> On Thu, Nov 4, 2010 at 11:27 AM, Kendall Gifford <zettabyte@gmail.com> wrote:
>>>>> On Thu, Nov 4, 2010 at 5:46 AM, Mike Cargal <mike@cargal.net> wrote:
>>>>>> regex = /^(A(?!A)|B(?!B)|C(?!C)|D{1,2}(?!D))+$/
>>>>>> 
>>>>>> ["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' =>
>>>>>> ==============
>>>>> 
>>>>> However, this also appears by my test to match "DADD", "ABA", etc:
>>>>> 
>>>>> ["ABA", "DADD", "CAC"].each do |string|
>>>>> puts "'#{string}' => #{string.match(regex)}"
>>>>> end
>>>>> 'DADD' => DADD
>>>>> 'ABA' => ABA
>>>>> 'CAC' => CAC
>>>>> 
>>>>> It does get you closer though. I rarely remember to make use of
>>>>> look-ahead (and look-behind and other "(?X" style patterns) since when
>>>>> switching languages/regexp engines, I'm never sure what features will
>>>>> be there (and will still work the same). I guess I'm too conservative,
>>>>> sticking with core/basic features.
>>>>> 
>>>>> This does make me curious how short of a regex using these features
>>>>> could be written for this one case...
>>>>> 
>>>> 
>>>> Okay, now this is even closer:
>>>> 
>>>> regex = /^(A(?=[^A]+$)|B(?=[^B]+$)|C(?=[^C]+$)|D{1,2}(?!D))+$/
>>>> 
>>>> However, it still has problems with "DADD", "DADBD" and such...
>>>> 
>>>> --
>>>> Kendall Gifford
>>>> zettabyte@gmail.com
>>>> 
>>> 
>>> 
>>> Oh... missed that detail... I *think* this covers the bases...
>>> 
>>> 
>>> regex = /^(A(?!.*A)|B(?!.*B)|C(?!.*C)|D{1,2}(?!.*D))+$/
>>> 
>>> ["ABCDD","CA","CAD",
>>> "CADD","CADDD","DAD",
>>> "BAC","BBAD","AABCCD",
>>> "DADD","DADBD","ABCDDA",
>>> "MIKE"].each do |string|
>>>  puts "'#{string}' => #{string.match(regex)}"
>>> end
>>> ====================
>>> 'ABCDD' => ABCDD
>>> 'CA' => CA
>>> 'CAD' => CAD
>>> 'CADD' => CADD
>>> 'CADDD' =>
>>> 'DAD' =>
>>> 'BAC' => BAC
>>> 'BBAD' =>
>>> 'AABCCD' =>
>>> 'DADD' =>
>>> 'DADBD' =>
>>> 'ABCDDA' =>
>>> 'MIKE' =>
>>> ====================
>>> 
>>> Mike Cargal
>>> 
>>> mike@cargal.net
>>> http://blog.mikecargal.com
>>> 
>> 
>> Except that "DAD" *is* legal according to OP's description. :-)
>> 
>> -- 
>> Kendall Gifford
>> zettabyte@gmail.com
>> 
> 
> Mike Cargal
> 
> mike@cargal.net
> http://blog.mikecargal.com
> 
> 
> 
> 
> 

Mike Cargal

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