• Matrix::value_type, VecX::value_type, and VecY::value_type must be the same type
• the multiplication operator must be defined for Matrix::value_type
• the addition operator must be defined for Matrix::value_type

• A.nrows() <= x.size()
• A.ncols() <= y.size()
• A has rectangle shape and is dense

  typedef matrix< double,
                  rectangle<>,
                  dense<>,
                  column_major >::type Matrix;
  typedef Matrix::size_type sizeT;
  const sizeT M = 4, N = 3;
  Matrix A(M, N);
  dense1D<double> x(M), y(N);
  double alpha = 1.0;
  // fill A, x, and y ...
  rank_one_update(A, scaled(x, alpha), y);