[LC++]Containers of Containers

[Paul M Foster]

I'm looking at creating a program to read various configuration files,
with various syntaxes. I can use flex et al to parse the various config
syntaxes, but all of them share the characteristic of having a name
equal some value. In some cases, config files will yield nested
name/value pairs, like Windows ini files. As in:

computer {
	chassis = ATX
	hard_drive {
		type = SCSI
		capacity = 40G
	}
	mouse = optical
}

Such nesting could go on presumably ad infinitum. The problem is this:
I'd like to represent the various "configurations" in a file as C++
classes, which might contain other configurations, which might contain
other configurations. Each configuration would potentially contain an
array (vector, list) of values. Like this:

class cfg {
	string name;
	...
	list<int> values;
	...
}

But that won't work for configs which contain strings instead of ints,
like this:

class cfg {
	string name;
	...
	list<string> values;
	...
}

Worse, it won't work for "nested" configs (where a config contains a
list of other configs). I thought about a template, where you specify
the type that the class will contain. But that won't work, because if
you have a cfg that contains a list of cfg objects, at some point in the
hierarchy, you're going to have to specify ints, strings or bools.

I could specify what's being contained as a union, like:

union opt_value {
	string *s;
	bool b;
	int i;
	float f;
	cfg *c;
};

But I'm not keen on using unions. Anyone have any ideas on how to do
this? (Sorry if this isn't clear. I'll elaborate, if needed.)

Paul