function skeleton2 ( )

%*****************************************************************************80
%
%% skeleton2 is an outline for completing exercise2.
%
%  Licensing:
%
%    This code is distributed under the GNU LGPL license.
%
%  Modified:
%
%    16 July 2020
%
%  Author:
%
%    John Burkardt
%
  fprintf ( 1, '\n' );
  fprintf ( 1, 'skeleton2:\n' );
  fprintf ( 1, '  Set up the linear system for the tiny Poisson problem.\n' );

  a = ?
  b = ?
  c = ?
  d = ?
  nx = ?
  ny = ?
  hx = ?
  x = ?
  hy = ?
  y = ?

  A = zeros(?,?);  
  rhs = zeros(?,1);

  k = 0;
  for j = 1 : ny
    for i = 1 : nx
      k = k + 1;
      if ( boundary )  % what values of i and j mean we are on the boundary?
        A(k,k) = ?
        rhs(k) = ?
      else
        CENTER = k;
        A(k,CENTER) = ?
        WEST = ?      % Work out the (i,j) coordinates of WEST, and use k_from_ij().
        A(k,WEST) = ?
        EAST = ?
        A(k,EAST) = ?
        SOUTH = ?
        A(k,SOUTH) = ?
        NORTH = ?
        A(k,NORTH) = ?
        rhs(k) = ?
      end
    end
  end
  
  u = A \ rhs

  return
end
function value = f ( x, y )

%*****************************************************************************80
%
%% f returns the right hand side of the Poisson equation.
%
  value = ?
  return
end
function value = g ( x, y )

%*****************************************************************************80
%
%% g returns the exact solution of the Poisson equation.
%
  value = ?
  return
end
