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: get_distance.m
    path of file: ./repos/CanlabCore/CanlabCore/External/spider/basic/@distance
    
    the code of the file until where you have to start completion: function [KM] = calc(k,d1,d2,ind1,ind2)
 
% [KM] = calc(k,d1,[d2],[ind1],[ind2])
%
% Calculate the distance with specific indexed data from 

    
function [KM] = calc(k,d1,d2,ind1,ind2)
 
% [KM] = calc(k,d1,[d2],[ind1],[ind2])
%
% Calculate the distance with specific indexed data from 
% datasets d1 and (optionally) d2.
% If d2 is not given it is assumed to make the matrix between d1 and itself
  
  global caching_kernel;

  if nargin<3, d2=[];end