/*
* This function takes the set difference of two sets.
* @param b: the set with which the set difference operation is to be done.
* @return c: the set formed after the set difference operation.
*/
set set_set_difference(set b)
{
/*
* first the difference of b with current set is taken.
* then, the difference of current set with b is taken.
* then, the union of second with first is taken.
*/
return set_difference(b).set_union(b.set_difference(*this));
}
