From: Hans Fugal <fugalh@...>
Date: 2006-03-13T06:23:45+09:00
Subject: Re: Regular Expression Intersection

Robert Klemme wrote:
> Benjohn Barnes <benjohn@fysh.org> wrote:
>> On 12 Mar 2006, at 09:58, Dan Kohn wrote:
>>
>>> You'll generally get a better answer if you include an example in
>>> your question.  Also, that link didn't work.
>>>
>>> If you're asking how to apply two regexps, you can use the scan
>>> method to get the results in arrays, and then intersect them with &.
> 
> This does not help at all as Benjon explains.  The question is not 
> whether there are some strings in a set of strings that are matched by 
> both RX but whether there is at least one string among *all* possible 
> strings that is matched by both.

....

> No.  He wants to know whether S(R1) & S(R2) is not empty.  At least 
> that's what he stated.  You might be able to solve the problem by 
> finding Ri but that was not the original problem stated.


Yes, precisely.

I figured out how to do it manually for this application which uses a 
simple regex syntax. Doing it for the Regexp class in general would be 
quite another thing.

Having now done it, I think it would make a great quiz, with a little 
head start (which I am willing to give). Are you listening James?

If anyone's interested in the solution I came up with let me know.