title: error: pointer to incomplete class type is not allowed
body: <p>I am stumped at this step while implementing a ternary tree:</p>
  
  <pre><code>#include&lt;stdio.h&gt;
  #include&lt;string.h&gt;
  #include&lt;stdlib.h&gt;
  
  typedef struct tnode *Tptr;
      typedef struct node
  {
      char splitchar;
      Tptr lokid,eqkid,hikid;
  
  }Tnode;
  
  int research(Tptr p,char *s)
  {
      if (!p) return 0;
      if (*s&lt;p-&gt;
  }
  
  int main(){
      return 0;
  }
  </code></pre>
  
  <p>When I move the mouse icon near the <code>p</code>, it shows me a red color and error:</p>
  
  <pre><code>pointer to incomplete class type is not allowed
  </code></pre>
  
  <p>My question is exactly what is an incomplete class? Please help me, thanks.</p>