nt formula)</li></ul></div><pre class="codeinput"><span class="keyword">classdef</span> ContactForceT_Spring &lt; ContactForceT
</pre><h2 id="2">Public properties</h2><pre class="codeinput">    properties (SetAccess = public, GetAccess = public)
        <span class="comment">% Formulation options</span>
        auto_stiff <span class="string">logical</span> <span class="string">=</span> <span class="string">logical.empty</span>;   <span class="comment">% flag for computing stiffness coefficient automaticall