compare shared_ptr object equality

Question

Is there an standard predicate to compare shared_ptr managed objects for equality.

template<typename T, typename U>
inline bool target_equal(const T& lhs, const U& rhs)
{
    if(lhs && rhs)
    {
        return *lhs == *rhs;
    }
    else
    {
        return !lhs && !rhs;
    }
}

I want something similar to the above code, but will avoid defining it my self if there is already a standard solution.

Answer 1

No, there isn't a standard solution. The equality operator of shared_ptr and the like compares only the pointers not the managed objects. Your solution is fine. I propose this version that checks if the pointed object is the same and returns false if one of the shared pointers is null and the other one it is not:

template<class T, class U>
bool compare_shared_ptr(const std::shared_ptr<T>&a,const std::shared_ptr<U>&b)
{
  if(a == b) return true;
  if(a && b) return *a == *b;
  return false;
}

Answer 2

No, there isn't such a predicate. An alternative is to use lambda function - but you still need to define it yourself.