function A=Laplacian(m,d)
% LAPLACIAN computes a negative finite difference Laplacian.
%   A=Laplacian(m,d) computes a negative finite difference Laplacian on
%   an interval/square/cube (d=1,2,3) using m interior points.
%   Notice that the mesh size is not included in A. 
    
if d==2
  G=numgrid('S',m+2); A=delsq(G); % Matlab way to construct 2D Laplacian
else
  error('not implemented yet, see Problem 2')
end
