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: covPeriodicNoDC.m
    path of file: ./repos/bads/gpml-matlab-v3.6-2015-07-07/cov
    
    the code of the file until where you have to start completion: function K = covPeriodicNoDC(hyp, x, z, i)

% Stationary covariance function for a smooth periodic function, with period p:
%
% k(x,x') = sf^2 * [k0(pi*(x-x')/p) - f(ell)] / [1 - f(ell)]
%        with
    
function K = covD(D,ell)                   % evaluate covariances from distances
  if ell>1e4                                              % limit for ell->infty
    K = cos(D);
  elseif 1/ell^2<3.75
    K = exp(cos(D)/ell^2);
    b0 = besseli(0,1/ell^2);
    K = (K-b0)/(exp(1/ell^2)-b0);
  else
    K = exp((cos(D)-1)/ell^2);
    b0 = embi0(1/ell^2);
    K = (K-b0)/(1-b0);
  end