code: function symbol(id, bp) {
  
  // Make a symbol if it does not already exist in the language's syntax.
  
      var the_symbol = syntax[id];
      if (the_symbol === undefined) {
          the_symbol = empty();
          the_symbol.id = id;
          the_symbol.lbp = bp || 0;
          syntax[id] = the_symbol;
      }
      return the_symbol;
  }
docs: These functions are used to specify the grammar of our language: