[Boost-users] regex iterator question

Subject: [Boost-users] regex iterator question
From: Robert Ramey (ramey_at_[hidden])
Date: 2009-03-30 02:25:52

I've got a need for regex and I would like to use it to extract tokens 
matching a regular expresssion from a file stream.  Seems like this would be 
a common desire.

So first shot is

boost::regex_token_iterator<some_input_iterator>

This doesn't work since regex_token_iterator requires a bidirectional 
iterator.  Seems reasonable enough.

So next I comb through boost and find

#include <boost/spirit/iterator/multi_pass.hpp>

and try

boost::regex_token_iterator<
    boost::spirit::multi_pass<some_input_iterator>
>

I'm thinking this is veeeeeery cool - maybe a 1000 lines of free code 
included for the price of one.

But, doesn't work.  multi_pass is a forward_trasversal iterator while 
regex_token_iterator requires a bidirectional_trasversal_iterator.  A huge 
disappoint to come soooo close.

Thinking about it, this problem must come very often.  How is it usually 
addressed?  There must be a simple bridge across this.  In a pinch, I'll 
just have to load the whole file into some sort collection, but I prefer the 
ultimate unlimited file size solution.

Robert Ramey