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: pr_spm_diff.m
    path of file: ./repos/malini/Codes/deconvolution - model/spm8/marsbar-0.44/@mardo_5/private
    
    the code of the file until where you have to start completion: function [J] = pr_spm_diff(varargin)
% matrix high-order differentials

    
function [J] = pr_spm_diff(varargin)
% matrix high-order differentials
% FORMAT [dfdx] = pr_spm_diff(f,x,...,n)
%
% f      - [inline] function f(x{1},...)
% x      - input argument[s]
% n      - arguments to differentiate w.r.t.
%
% dfdx          - df/dx{i}                     ; n =  i
% dfdx{p}...{q} - df/dx{i}dx{j}(q)...dx{k}(p)  ; n = [i j ... k]
%
% - a cunning recursive routine
%__________________________________________________________________________
% Copyright (C) 2005 Wellcome Department of Imaging Neuroscience

% Karl Friston
% $Id: spm_diff.m 417 2006-02-01 13:50:14Z karl $

% create inline object
%--------------------------------------------------------------------------
f     = fcnchk(varargin{1});
x     = varargin(2:(end