[Boost-users] Boost.MultiArray + iterators

From: Dennis Zickefoose (dennis.zickefoose_at_[hidden])
Date: 2005-11-06 01:29:33

I have a simple two dimensional multi_array that I am trying to copy a
row out of.  This works, but I get a warning about a type conversion
that I would like to get rid of.  Example:

boost::multi_array<double, 2> array(boost::extents[42][42]);
std::vector<double> row(array[0].begin(), array[0].end());

This produces the following warning in VC++ 7.1:
c:\Boost\include\boost-1_33\boost\multi_array\iterator.hpp(149) :
warning C4244: '+=' : conversion from 
'boost::detail::multi_array::array_iterator<T,TPtr,NumDims,Reference>::difference_type'
to
'boost::detail::multi_array::array_iterator<T,TPtr,NumDims,Reference>::index',
possible loss of data

This is followed by a long string of support messages that ultimately
point to the vector initialization.  Yet the vector is successfully 
initialized with the range of values I expect.  So what am I doing wrong 
here?  I understand that [array.begin(), array.end()) is actually a 
range of sub-views, rather than a range of values...is this a side 
effect of this distinction?

At the moment, I have replaced that with &array[0][0] to avoid the 
warning, but if possible I would like to go with the more reliable 
iterator interface in the future.

Any suggestions/advice would be greatly appreciated.

DZJr