anchor.diff:  
   %% =====================================================================
   %% @spec pos_to_var_name(Node::syntaxTree(), Pos::{integer(), integer()})->
  -%%                      {ok, {VarName,DefPos, Category}} | {error, none}
  +%%                      {ok, {VarName,DefPos, Category}} | {error, string()}
   %%
   %%      VarName = atom()
   %%      DefPos = [{integer(), integer()}]
  
positive.code: 
  %% =====================================================================
  %% @spec pos_to_expr(Tree::syntaxTree(), Start::Pos, End::Pos) ->
  %%                  {ok, syntaxTree()} | {error, none}
  %%
  %%       Pos={integer(), integer()}
  %% @doc Get the largest, left-most expression enclosed by the start and end locations.
  
negative.code: 
  %%============================================================================
  %% @spec pos_to_fun_def(Node::syntaxTree(), Pos::{integer(), integer()}) 
  %%                     -> {ok, syntaxTree()} | {error, string()}
  %% @doc Get the AST representation of the function definition in which the 
  %% location specified by Pos falls.
  %%               
  %% @see pos_to_fun_name/2.
  
  -spec(pos_to_fun_def(Node::syntaxTree(), Pos::pos()) 
                       -> {ok, syntaxTree()} | {error, string()}).
  pos_to_fun_def(Node, Pos) ->
      case once_tdTU(fun pos_to_fun_def_1/2, Node, Pos) of
        {_, false} -> {error, "You have not selected a function definition!"};
        {R, true} -> {ok, R}
      end.
  
  