code: function precedence(ast) {
    var p = PRECEDENCE[ast["type"]];
    if ( _.isNumber(p) ) // represents Fixnum? I'm so sorry.
      return p;
    else if ( p && p.constructor === Object ) // p is a {} object
      return p[ast["operator"]];
    else
      return 0;
  }
docs: Returns the precedence of operator represented by given AST node