Re: [Chicken-users] irregex and callbacks

[Alex Shinn]

On Thu, Oct 2, 2014 at 10:05 PM, Peter Bex <address@hidden> wrote:

On Thu, Oct 02, 2014 at 01:47:15PM +0100, Andy Bennett wrote:
> Hi,
>
> > You could use submatch info and check which submatch matched.
> > This would keep the matching as a single regexp, but you'd then
> > need a linear scan to see which submatch succeeded.
>
> Thanks Alex!
>
> I'm trying to avoid the linear scan as there are several tens of
> thousand entries in the database. How expensive do you think it would be?

My guess is that it will fall back to a backtracking parser, as this would
certainly exceed the DFA compiler's size limit.  And that's going to be
extremely slow!

You could force DFA compilation, assuming the patterns

don't use any features that require backtracking, and assuming

there's no exponential explosion of states.  Compilation would

still be slow but execution would be fast.  You'd require some

internal help (checking tags in the final state) to quickly check

which pattern matched though.

What are the patterns like?  A specialized solution might be

better here.

-- 

Alex