You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: laplacian.m
    path of file: ./repos/chebfun/@spherefun
    
    the code of the file until where you have to start completion: function f = laplacian(f) 
%LAPLACIAN   Scalar laplacian of a SPHEREFUN.
%   L = LAPLACIAN(F) computes the spherical Laplacian of the SPHEREFUN F.  
%  
% This is gvien, in intrinsic spherical coordinates as
% 
% laplacian(F) = d_{theta} d_{theta} F + tan(theta) d_{theta} F + 
%                1/sin(theta) + d_{lambda} d_{lambda} F
%

    
function f = laplacian(f) 
%LAPLACIAN   Scalar laplacian of a SPHEREFUN.
%   L = LAPLACIAN(F) computes the spherical Laplacian of the SPHEREFUN F.  
%  
% This is gvien, in intrinsic spherical coordinates as
% 
% laplacian(F) = d_{theta} d_{theta} F + tan(theta) d_{theta} F + 
%                1/sin(theta) + d_{lambda} d_{lambda} F
%
% where 0 <= theta <= pi is the co-latitude variable and 
% -pi <= lambda <= pi  is the longitude variable.
%
% See also GRADIENT, DIVERGENCE.

% Copyright 2017 by The University of Oxford and The Chebfun Developers.
% See http://www.chebfun.org/ for Chebfun information.

% We implement the computation of the Laplacian using the spherefun/diff
% command.  This function computes tangential derivatives in the x, y, and
% z directions, so that the Laplacian can be implemented as we usually
% think of it in 3D, i.e.
% laplacian(f) = f_xx + f_yy + f_zz.

% Compute the derivatives
fxx = diff(f, 1, 2); 
fyy = diff(f, 2, 2); 
fzz = diff(f, 3, 2);

% Determine which derivative has the most coefficients in its
% representation for the columns and rows.
[mxx,nxx] = length(fxx);
[myy,nyy] = length(fyy);
[mzz,nzz] = length(fzz);

m = max([mxx myy mzz]);
n = max([nxx nyy nzz]);

% Ensure m and n are even:
m = m + mod(m, 2);
n = n + mod(n, 2);

% Construct a spherefun by sampling the derivatives on the same size grid.
f = spherefun(sample(fxx, m, n/2) + sample(fyy, m, n/2) + ...
               sample(fzz, m, n/2));

end