title: Bison passing back resulting AST
body: <p>In <a href="http://www.hwaci.com/sw/lemon/" rel="nofollow">lemon</a> I was able to use the third parameter of the parsing function to pass back the result to the caller when the starting symbol was reduced.</p>
  
  <p>How would I do the same in bison? Is it enough to assign that value to $$ within the starting symbol's action code, and from the caller to take it as the "yy minor" value, after the final call to <code>yypush_parse()</code>?</p>
  
  <p>The parser is push and pure. Thread-safety is a must.</p>