s="k">interface  </span>
<span class="k">    pure type</span><span class="p">(</span><span class="n">spectrum_type</span><span class="p">)</span> <span class="k">function </span><span class="n">func</span><span class="p">(</span><span class="n">initial</span><span class="p">,</span><span class="n">tendency</span><span class="p">,</span><span class="n">dt</span><span class="p">)</span>
      <span class="k">import</span> <span class="kd">::</span> <span class="n">spectrum_type</span><span class="p">,</span><