anchor.diff:  
   %% Scanning Erlang code.
   
  --spec scan_erl_exprs(prompt()) -> erl_scan:tokens_result().
  +-spec scan_erl_exprs(prompt()) -> erl_scan:tokens_result() | request_error().
    
   scan_erl_exprs(Prompt) ->
       scan_erl_exprs(default_input(), Prompt, 1).
   
  --spec scan_erl_exprs(device(), prompt()) -> erl_scan:tokens_result().
  +-spec scan_erl_exprs(device(), prompt()) -> erl_scan:tokens_result() | request_error().
   
   scan_erl_exprs(Io, Prompt) ->
       scan_erl_exprs(Io, Prompt, 1).
   
  --spec scan_erl_exprs(device(), prompt(), line()) -> erl_scan:tokens_result().
  +-spec scan_erl_exprs(device(), prompt(), line()) -> erl_scan:tokens_result() | request_error().
   
   scan_erl_exprs(Io, Prompt, Pos0) ->
       request(Io, {get_until,unicode,Prompt,erl_scan,tokens,[Pos0]}).
   
  --spec scan_erl_form(prompt()) -> erl_scan:tokens_result().
  +-spec scan_erl_form(prompt()) -> erl_scan:tokens_result() | request_error().
   
   scan_erl_form(Prompt) ->
       scan_erl_form(default_input(), Prompt, 1).
   
  --spec scan_erl_form(device(), prompt()) -> erl_scan:tokens_result().
  +-spec scan_erl_form(device(), prompt()) -> erl_scan:tokens_result() | request_error().
   
   scan_erl_form(Io, Prompt) ->
       scan_erl_form(Io, Prompt, 1).
   
  --spec scan_erl_form(device(), prompt(), line()) -> erl_scan:tokens_result().
  +-spec scan_erl_form(device(), prompt(), line()) -> erl_scan:tokens_result() | request_error().
   
   scan_erl_form(Io, Prompt, Pos0) ->
       request(Io, {get_until,unicode,Prompt,erl_scan,tokens,[Pos0]}).
  
positive.code: 
  -type parse_form_ret() :: {'ok', erl_parse_absform(), line()}
                          | {'eof', line()}
                          | {'error', erl_scan:error_info(), line()}.
  
  -spec parse_erl_form(prompt()) -> parse_form_ret().
  
  
negative.code: 
  -type parse_ret() :: {'ok', erl_parse_expr_list(), line()}
                     | {'eof', line()}
                     | {'error', erl_scan:error_info(), line()}
                     | request_error().
  
  -spec parse_erl_exprs(prompt()) -> parse_ret().
  
  