[boost] [iterator] zip_iterator equality comparison

Subject: [boost] [iterator] zip_iterator equality comparison
From: Jeremiah Willcock (jewillco_at_[hidden])
Date: 2009-07-05 16:10:03

It is standard in STL to have two ranges that are zipped together (such as 
in the two-input-sequence version of std::transform at 
http://www.sgi.com/tech/stl/transform.html) where the first range has 
begin and end iterators and other ranges have only begin iterators. 
However, boost::zip_iterator does not support this capability because it 
compares all iterators in the iterator tuple.  Therefore, it is not 
possible to write std::transform on two sequences by using a zip_iterator 
to join the sequences.  Allowing this by only comparing the first elements 
in the iterator tuples would simplify the code for zip_iterator, although 
it would no longer allow the zipping of zero sequences unless that was 
special-cased.  Is this a reasonable feature to allow?  I could probably 
put together a patch for it in the next few days if people wanted it.

-- Jeremiah Willcock