 need to be defined only if NANLN&gt;0 (otherwise it is assumed that all matrix
            constraints are linear and thus their 2nd derivatives are zeros). Only one of these will be used, if both are defined, <tt>mconlagrhess()</tt> will be chosen. Note that although the return values are symmetric matrices, <b>both</b> triangles need to be present.
         </p><pre>   function [Ak,     userdata] = mconfun(x,Y,k,userdata)
   function [dAki,   userdata] = mcongrad(x,Y,k,i,userdata)
   function [ddAkij, us