illegal value</span>
<span class="w">   </span><span class="k">if</span><span class="p">(</span><span class="nb">len</span><span class="p">.</span><span class="n">lt</span><span class="p">.</span><span class="mi">1</span><span class="p">)</span><span class="k">then</span>
<span class="k">      write</span><span class="p">(</span><span class="o">*</span><span class="p">,</span><span class="o">*</span><span class="p">)</span><span class="s1">&#39;*mat_rat* internal error -- len&lt;1&#39;</span>
<span class="w