using C++ to define new functions

Hello,

    Sorry to disturb the hacker list for a question that seems not so hard.
But I got no answers elsewhere...
    Is is definitively impossible to use C++ to define new SQL functions or operators
in SQL ? (I need this in order to use a big geometric library, to produce e.g. polygon
intersections, or harder).

           I manage to add C functions, with a

           create function ... returns .. as language 'c';

 but the linking style of c++ is rather different.
Do you have an idea ?

Thanks,

David
dgross@lri.fr