 
    <code>xsplineTangentExpr</code> for the scenario above.
  </p>
<div class="chunk" id="unnamed-chunk-8"><div class="rcode"><div class="source"><pre class="knitr r"><span class="hl kwd">xsplineTangentExpr</span><span class="hl std">(</span><span class="hl kwd">xsplineFunGenerator</span><span class="hl std">(</span><span class="hl str">&quot;s1neg&quot;</span><span class="hl std">,</span> <span class="hl str">&quot;s2neg&quot;</span><span class="hl std">,</span> <span class="hl str">&quot;noA0&quot;</spa