Re: [Boost-users] Boost.MultiArray + iterators

From: Ronald Garcia (garcia_at_[hidden])
Date: 2005-11-12 10:22:52

Hi Dennis,

I don't have access to VC++ 7.1 at the moment and cannot recreate the  
error you are seeing on my platform.  Could you try applying the  
following patch to boost/multi_array/types.hpp and let me know if this  
does the trick?

Thanks,
ron

*** types.hpp	01 Dec 2003 14:07:10 -0500	1.3
--- types.hpp	12 Nov 2005 10:19:48 -0500	
***************
*** 26,32 ****

   // needed typedefs
   typedef std::size_t size_type;
! typedef int index;

   } // namespace multi_array
   } // namespace detail
--- 26,32 ----

   // needed typedefs
   typedef std::size_t size_type;
! typedef std::ptrdiff_t index;

   } // namespace multi_array
   } // namespace detail

On Nov 6, 2005, at 1:29 AM, Dennis Zickefoose wrote:

> 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
>
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