[C++-sig] How to extract a sublist from a list in C++ ?

[PJ Durai]

Greetings,

I couldnt figure out the following bit.

Say I am passing a list of lists.   [ [a, b] , [c,d]]  to a method in a C++ 
object.

In the C++ class,

void ParseList (list lst)
{
   object o = lst[0];
   // how do I conver 'o' to a list again?
   list l1  = extract<list> (o);   <- naive attempt. but doesnt work.
}

Appreciate your time.

thanks
pj