[boost] Re: io operations for stl containers?

From: Jason House (jhouse_at_[hidden])
Date: 2003-02-05 11:01:30

Terje Slettebø wrote:

> > It should handle maps and pairs
> > reasonably well.  I think that I have the same complaints about this as
> > io_manip
> >
> > The saving of information to the stream means that you can affect all
> > future output...
> >
> > For instance, if you have a type
> > map<custom_object, list<string> >
> >
> > and custom_object's stream output uses io_format<list<string> >, then
> > you are going to run into trouble if it wants a different formatting.
>
> Right. That's a consequence of this. As you say too, I don't know any
> obvious alternatives, though.
>

I thought of one thing that might work reasonably well.

How about making ++io_format< T > save the current format in a stack.
and having io_format< T>-- restore the previously queuued format

so, then something like

> > std::cout << ++io_format<char (&)[3]>("\n|","|\n","|")--
> >           << ++io_format<char (&)[3][3]>("-------","-------","-------")--
> >           << board << '\n';

would save and restore the formating for char(&)[3][3] and char(&)[3] and never
stomp on anything else.

The net effect is that you can optionally add the extra few characters and prevent
stomping on other code that is displaying your class.