From: Nikolai Weibull <mailing-lists.ruby-core@...>
Date: 2005-11-04T07:47:00+09:00
Subject: Re: [RFC] Method of feeding input to regexp matching

David A. Black wrote:

> > I would very much like to be able to provide a Regexp object input
> > from some input source other than a "fixed" string.  Examples of
> > such sources would be a file bufferer that reads chunks from a file
> > and can then make them accessible to the Regexp object as it needs
> > them.  At the moment there's no way to do this.  The exact semantics
> > of such a method might be quite complicated, as it can be hard to
> > maintain the MatchData.  How this is to be done is beyond this
> > initial query, but I would like to know if anyone besides me sees
> > any merit in this.

> We did this in scanf.rb; you can scanf a stream as well as a string.
> I suspect that arbitrary regular expressions would be a lot harder to
> do this with than scanf format specifiers (which are not too easy
> themselves), especially if you got into backtracking and alternation
> and (non-)greediness and so forth.  But as long as the stream was
> rewindable that might not be too great an obstacle.

True.  One solution would be to keep data around as long as its needed.
All we���re doing is generating the string on-the-fly, sort of.  Or am I
missing something in your reasoning?  

This is also a good reason _not_ to have a backtracking engine, but I
guess that���s another battle.

        nikolai

-- 
Nikolai Weibull: now available free of charge at http://bitwi.se/!
Born in Chicago, IL USA; currently residing in Gothenburg, Sweden.
main(){printf(&linux["\021%six\012\0"],(linux)["have"]+"fun"-97);}