Re: [Boost-users] How to inherit from boost::multi_array

From: Ronald Garcia (garcia_at_[hidden])
Date: 2005-06-13 09:54:01

Greetings Yan,

I do not recall the context of the problem you describe below, but It 
appears that the definition:

> Array (const Array& other) :
>  boost::multi_array<double, 2> (other)
>  {}

is the problem.  the above expression will call the templated 
constructor.  I believe that the solution here is to cast "other" to 
the multi_array type.  That should result in the proper constructor 
call.

HTH,
ron

On Jun 6, 2005, at 12:09 PM, Yan Zhang wrote:

> I’m read the posting by Thomas and replay by Ronald on how to inherit 
> from boost::multi_array as following:
>  
>  
> On Oct 2, 2004, at 10:26 AM, Thomas Mensch wrote:
>  
> Dear List,
>  
> I am using boost 1.31.0 on Linux (with gcc 3.3.2)
> I would like to create a 2D array class, which inherits  from
> boost::multi_array<double, 2> class. However I have problems
> with the copy constructor of my class Array.  Below is the code,
> which I am trying to run.
>  
> #include <boost/multi_array.hpp>
>
>  class Array
>  : public boost::multi_array<double,2>
>  {
>  public:
>  Array (void) :
>  boost::multi_array<double, 2> ()
>  {}
>
>  Array (const int nrow, const int ncol) :
>  boost::multi_array<double, 2> (boost::extents[nrow][ncol])
>  {}
>
>  Array (const Array& other) :
>  boost::multi_array<double, 2> (other)
>  {}
>
>  ~Array (void)
>  {}
>
>  Array& operator= (const Array& rhs)
>  {
>  if (&rhs != this)
>  {
>  boost::multi_array<double, 2>::operator= (rhs);
>  }
>  return *this;
>  }
>  }; /* class Array */
>  
>  
>
> Ronald’s replay:
>
> Greetings Thomas,
>
>  Though you did not supply the error message from your compiler, I 
> suspect that the problem is this: multi_array has a templated 
> constructor of the form:
>  template <class T> multi_array(T const&);
>
>  that will match your Array type better than the constructor with the 
> signature:
>
>  multi_array(multi_array<double,2> const&);
>
>  In short, overload resolution is not selecting the constructor that 
> you desire. You'll need to coerce your Array reference to a 
> multi_array<double,2> reference before passing it to the constructor.
>
>  Hope this helps.
>
>
> I had the same problem as Thomas’. I don’t quit understand Ronald’s 
> comment. How to you overload template <class T> multi_array(T const&) 
> instead of multi_array(multi_array<double,2> const&)? I thought 
> Thomas’ code is overloading template <class T> multi_array(T const&).
>
>  
>
> Thanks in advance,
>
>  
>
> Yan
>
>  
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