c++ - Peeking the next element in STL container

Question

Is it possible to peek next element in a container which the iterator currently points to without changing the iterator?

For example in std::set,

int myArray[]= {1,2,3,4};
set <int> mySet(myArray, myArray+4);
set <int>::iterator iter = mySet.begin();

//peek the next element in set without changing iterator.

mySet.erase(iter); //erase the element if next element is n+1

Answer 1

C++0x adds a handy utility function, std::next, that copies an iterator, advances it, and returns the advanced iterator. You can easily write your own std::next implementation:

#include <iterator>

template <typename ForwardIt>
ForwardIt next(ForwardIt it, 
               typename std::iterator_traits<ForwardIt>::difference_type n = 1)
{
    std::advance(it, n);
    return it;
}

You can use this in your example like so:

if (iter != mySet.end() && next(iter) != mySet.end() && *next(iter) == *iter + 1)
    mySet.erase(iter);