C++ - Finding intersection of two ranges

simple answer is to just find end values of intersection range and then iterate over this range.

say for the range [l1, r1], [l2, r2] intersection between them can be calculated as:

 if ((r1 < l2) ||  (r2 < l1)) then no intersection exits.
 else l = max(l1, l2) and r = min(r1, r2)

just iterate over the range [l, r] to get the intersection values.

For the sake of completeness I would like to add a 'boost answer'.

If you're already using boost, you don't need to write your own code but can take the header-only

#include <boost/numeric/interval.hpp>

and use the intersect function dealing with the type interval<T>.

intersection = { std::max(arg1.min, arg2.min), std::min(arg1.max, arg2.max) };
if (intersection.max < intersection.min) {
  intersection.markAsEmpty();
}