Question

In what library/header (if any) is mathematical set defined? I need set to have functions like intersection, union etc.

Answer 1

Use <set> and <algorithm>.

Then the std provides std::set_union, std::set_intersection and so on.

example:

#include <set>
#include <algorithm>

 ...
std::set<int> s1, s2;
for(int i = 0; i < 20; ++i)  s1.insert(i);
for(int i = 10; i < 30; ++i) s2.insert(i);
std::set<int> my_union, my_intersection;
std::set_union(s1.begin(), s1.end(), s2.begin(), s2.end(), std::inserter(my_union, my_union.begin()));
std::set_interesction(s1.begin(), s1.end(), s2.begin(), s2.end(), std::inserter(my_intersection, my_intersection.begin()));