Set with custom compare

In my project I use std::set with custom Compare function for maintaining an event queue. It fulfills following criteria:

• event duplication is not allowed

• should maintain the insertion order

(tried std::vector first, but that performed poorly because of complicated duplicate removal)

The important code is:

template 
class EventQueue {
public:
  EventQueue() : set_(std::set()) {}
  void Insert(T elem) {
    set_.insert(DataWrap(elem, set_.size()));
  }

  // ....

private:
  struct DataWrap {
    T data;
    unsigned int order;
    DataWrap(T d, unsigned int o) : data(d), order(o) {}
    bool operator set_;
};

Naturally I want to avoid undefined behaviour. As far as I can see my Compare fulfills the requirements of strick weak ordering (irreflexive, transitive, asymetric)

Can you confirm that this code is well-defined, or am I missing something? Thanks for your time!

As a side note, you pass the element by copy not by const reference. This might also have some real preformance effects. SO rather do

void Insert(const T&)

Also you could use emplace_back to enable inplace construction of the elements in the vector. On the other hand std::find only takes const T& so I would guess, that move semantics do not really buy you anything here.

StackExchange Code Review Q#159428, answer score: 2