public T Do(IStack <T> cmd, T input)
{
var output = cmd.Do(input);
_undo.Push(cmd);
_redo.Clear();
return(output);
}
public T Redo(T input)
{
if (_redo.Count > 0)
{
IStack <T> cmd = _redo.Pop();
T output = cmd.Do(input);
_undo.Push(cmd);
return(output);
}
return(input);
}