Re: [Regexp] Finding failure point in RE

[Wes Biggs]

Mitch, that's not going to work as is.  Take out the "if" block around 
firstToken.match(); it's OK if this returns false (no full match).  Still not 
guaranteeing it will work, though. :-)

public int getLengthMatched(Object o, int index, int eflags) {
   CharIndexed input = makeCharIndexed(o, index);
   if (firstToken == null)  { return 0; } // Trivial case of empty regexp
   REMatch m = new REMatch(numSubs, index, eflags);
   firstToken.match(input, m);
   int max = 0;
   while (m != null) {
     if (m.index > max) { max = m.index; }
     m = m.next;
   }
   return max;
 }




Claborn, Mitch wrote:

> Thanks Wes. 
>
> Yes, I am using isMatch().
>
> I'll give your code a try and report the results here.
>
> mitch
>
>
> -----Original Message-----
> From:
> address@hidden
> org
> [mailto:gnu-regexp-users-bounces+mitch-keyword-gnuregexp.197863=claborn.
> address@hidden Behalf Of Wes Biggs
> Sent: Monday, July 26, 2004 4:19 PM
> To: 'address@hidden'
> Subject: Re: [Regexp] Finding failure point in RE
>
>
> mitch-GNU RegExp List wrote:
>
>  
>
> > I posted this question a while but got no response, so I'll try once
> >    
> more...
>  
>
> > Is there a way (or plans to develop a way) to discover where in a regular
> > expression that matching failed (i.e. didn't find a match)?  Or
> >    
> alternately,
>  
>
> > but not as useful, where in the regular expression is the last point that
> > successfully matched the input string?
> >
> > Background:  I created a system that uses regular expressions to match
> > against the contents of incoming emails that contain output from various
> > status checks, operational tasks, etc.  When a match fails, it is a time
> > consuming processes to discover where the failure point is.  A index into
> > the regular expression (or input string I guess) that showed where the
> >    
> match
>  
>
> > failed would be very useful and time saving.
> >
> >
> >    
>
> Hi Mitch -- the short answer is no, there is not currently a way or a 
> plan to implement this.
>
> I'm assuming you're applying this to a situation where you're using 
> isMatch() -- otherwise the logic gets a little ambiguous, because a 
> failed RE will fail at every point along the input.
>
> You could add a method like
> int RE::getLengthMatched(input)
> which would execute similarly to isMatch() but keep the contextual 
> information such that
> RE.isMatch(input) ==> (RE.getLengthMatched(input) == input.length())
>
> Here's some untested off-the-cuff code you can try adding to RE.java:
>
> public int getLengthMatched(Object o, int index, int eflags) {
>    CharIndexed input = makeCharIndexed(o, index);
>    if (firstToken == null)  { return 0; } // Trivial case of empty regexp
>    REMatch m = new REMatch(numSubs, index, eflags);
>    if (firstToken.match(input, m)) {
>     int max = 0;
>    while (m != null) {
>        if (m.index > max) { max = m.index; }
>        m = m.next;
>    }
>    }
>    return max;
>  }
>
>
>