r.get;
r.union;
r.and;
You're not calling the functions here.
r.get();
r.union(argument1, argument2);
r.and(argument1, argument2);
But your class already contains the vector arguments, a and b, if I understood. So you could skip them from the argument list altogether.
void union()
{
...
}
void and()
{
...
}
It's a bit of a mess as it is.