concepts.cpp

#include <iostream>
#include <list>
#include <vector>

/*

In the code below, we provide two implementations of the function increment().
The commented one is optimized for iterators which fulfill the requirements of
the concept RandomAccessIterator.

1. Uncomment and complete the concept RandomAccessIterator: check that the
   class IterT has operator +=.
2. Find an existing concept in the standard library, which can replace the
   previous user-defined concept.

*/

/*

template <typename IterT>
concept RandomAccessIterator = requires(... TO BE COMPLETED...) {
  ... TO BE COMPLETED...
};

template <RandomAccessIterator IterT>
void increment(IterT &iter, unsigned d) {
  iter += d;
  std::cout << "(random)\n";
}

*/

template <typename IterT>
void increment(IterT &iter, unsigned d) {
  while (d--)
    ++iter;
  std::cout << "(other)\n";
}

int main() {
  std::list<int> l_data = {1, 2, 3, 4, 5};
  auto l_itr = l_data.begin();
  increment(l_itr, 2);

  std::vector<int> v_data = {1, 2, 3, 4, 5};
  auto v_itr = v_data.begin();
  increment(v_itr, 2);
}