anchor.diff:    #enter: const [10],
     #backspace: const [127],
     #tab: const [9],
  +  #ctrlX: const [24],
     #delete: const [27, 91, 51, 126],
   };
   
  
positive.code:     _prompt.forwardspace();
    }
  
    void _updatePrompt(List<int> bytes, {onEnter(), onTab(),
        Map<Symbol, Function> keyCallbacks}) {
      if (_equalList(bytes, _keys[#enter])) onEnter();
      else if (_equalList(bytes, _keys[#tab])) onTab();
      else if (_keys.values.any((k) => _equalList(k, bytes))) {
        keyCallbacks[_keys.keys.firstWhere((s) => _equalList(_keys[s], bytes))]();
        _render();
  
negative.code:             c.add('help ${_prompt._content
                  .split(' ')
                  .first}'.trim());
            },
            onCtrlX: () {
              _write('\n');
              c.add('exit');
            },
            keyCallbacks: {
              #up: _onUp,
  