Re: 2 dimensional array within function

From:
"Giovanni Dicanio" <giovanni.dicanio@invalid.com>
Newsgroups:
microsoft.public.vc.mfc
Date:
Wed, 6 Feb 2008 16:38:05 +0100
Message-ID:
<OGwqvZNaIHA.2268@TK2MSFTNGP02.phx.gbl>
"David Wilkinson" <no-reply@effisols.com> ha scritto nel messaggio
news:uk4ziZKaIHA.484@TK2MSFTNGP06.phx.gbl...

Both these problems would not occur if you used std::vector.


I agree with David Wi.

std::vector, and STL containers in general, seem to offer better
"composibility" than MFC containers.

Moreover, if the purpose is to store a 2D matrix like MxN, then a viable
solution could be also to use a single std::vector (or even valarray), sized
M*N (rowCount * coumnCount), and provide a method to address each element,
converting from (row, column) pair index to a single index to access the
array, using a formula like this:

  index = col + row*columnCount

 e.g.

  template <typename T>
  class Matrix
  {
  public:
        explicit Matrix( int columnCount, int rowCount )
          : m_data( columnCount * rowCount ), // set matrix size
            m_columnCount( columnCount ),
            m_rowCount( rowCount )
        {}

      const T & at( int row, int column ) const
      {
         ASSERT( row >= 0 && row < m_rowCount );
         ASSERT( column >= 0 && column < m_columnCount );
         // Access specific element in 1D array
         // (convert from 2D (row, column) to 1D array index)
         return m_data.at( column + row * m_columnCount );
      }

      ...

  private:
     std::vector< T > m_data;
     int m_columnCount;
     int m_rowCount;
  };

Giovanni

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