ground/gcs/src/libs/eigen/doc/snippets/Tutorial_Map_using.cpp

   1 typedef Matrix<float,1,Dynamic> MatrixType;
   2 typedef Map<MatrixType> MapType;
   3 typedef Map<const MatrixType> MapTypeConst;   // a read-only map
   4 const int n_dims = 5;
   5
   6 MatrixType m1(n_dims), m2(n_dims);
   7 m1.setRandom();
   8 m2.setRandom();
   9 float *p = &m2(0);  // get the address storing the data for m2
  10 MapType m2map(p,m2.size());   // m2map shares data with m2
  11 MapTypeConst m2mapconst(p,m2.size());  // a read-only accessor for m2
  12
  13 cout << "m1: " << m1 << endl;
  14 cout << "m2: " << m2 << endl;
  15 cout << "Squared euclidean distance: " << (m1-m2).squaredNorm() << endl;
  16 cout << "Squared euclidean distance, using map: " <<
  17   (m1-m2map).squaredNorm() << endl;
  18 m2map(3) = 7;   // this will change m2, since they share the same array
  19 cout << "Updated m2: " << m2 << endl;
  20 cout << "m2 coefficient 2, constant accessor: " << m2mapconst(2) << endl;
  21 /* m2mapconst(2) = 5; */   // this yields a compile-time error