how to use std::find with an < operator that is not std::less

Question

say I have

class newVector: public std::vector<T> {
    public:
        bool operator< (const newVector& v) { 
            //..
        }
};

And

a std::set<newVector>; 

I can't manage to use a.find(...) properly, I am not sure what to put into the (...) in order to use newVector::operator<. When I just put a.find(element) it uses std::less. Should I change std::less somehow?

Answer 1

Ignoring for the time being that deriving from std::vector is a bad idea, I can think of the following ways to address the issue:

1. Define operator< for objects of newVector.

   class newVector: public std::vector<T> {
       public:
           bool operator< (const newVector& v) const { 
               //..
           }
   

   and

   std::set<newVector> a;
   a.find(...);
   

2. Define a functor that has appropriate operator() function and use it to create the std::set.

   template <typename T>
   struct NewVectorLess
   {
      bool operator()(newVector<T> const& lhs, newVector<T> const& rhs)
      {
        // ...
      }
   };
   

   and

   std::set<newVector<int>, NewVectorLess<int>> a;
   a.find(...);