y</span>

        <span class="comment">% Contact parameters</span>
        stiff <span class="string">double</span> <span class="string">=</span> <span class="string">double.empty</span>;   <span class="comment">% stiffness coefficient</span>
    <span class="keyword">end</span>
</pre><h2 id="3">Constructor method</h2><pre class="codeinput">    methods
        <span class="keyword">function</span> this = ContactForceT_Spring()
            this = this@ContactForceT(ContactForceT.SPRING);
            this = 