[Boost-users] Using filter_iterator in a for loop

From: David Ward (david.ward_at_[hidden])
Date: 2007-01-02 21:06:16

I want to use a boost::filter_iterator to iterate through a std::vector 
using a for-style loop.  I haven't been able to find any examples of the 
proper way to do this in the Boost documentation (or how to do this for any 
other Boost iterator, for that matter).

>From searching this newsgroup, I found that it is possible to do:

for (boost::filter_iterator< ... > iter(myVector.begin(), myVector.end());
    iter != boost::filter_iterator< ... >(myVector.end());
    ++iter )
{ ... }

However, iter is quite aware of when it has reached the end of the vector, 
since that is the second parameter in its constructor.  Is it really 
necessary to create a second filter_iterator, set it to the end of the 
vector, and then test iter against it?  Can't I somehow test iter alone to 
see if it has reached the end of the vector?

If I use std::for_each, it needs both a beginning and ending iterator as 
parameters, leading to the same situation as above.

I've also looked at the Boost Range library and BOOST_FOREACH (described at 
http://www.boost.org/regression-logs/cs-win32_metacomm/doc/html/foreach.html). 
However, from my understanding, I don't think either of these apply to or 
work with Boost iterators.

Whatever method is appropriate, I would ask that someone please exapnd the 
Boost iterator documentation to include an example of using Boost iterators 
in a for-style loop.  I feel that this is a very basic and common usage of 
iterators which was not addressed.  Thank you.

--
David Ward
Communications and Networking Division
Information Technology and Telecommunications Laboratory
Georgia Tech Research Institute