isLessThan function for structure with 7 integers
Don't re-invent the wheel (unless of course you want practice at doing that):


Instead of naming a bunch of elements that are all the same type, use an array for your structure's elements like std::array, or use a std::tuple. Or if you really don't want to change your structure's content, use std::tie to craft a tuple of your structure's elements on demand.
If you used a regular array use std::lexicographical_compare on the iterable elements of the two structures. A std::array or std::tuple already has non-member function support for operators like &lt;, &lt;=, &gt;=, etc. though. 
Kick back and enjoy a brewski. ;)  (only if allowed of course and be sure to drink responsibly etc. etc.).