// fig15_08.cpp
// Using concepts to select overloads.
#include <array>
#include <iostream>
#include <iterator>
#include <list>

// calculate the distance (number of items) between two iterators 
// using input iterators; requires incrementing between iterators, 
// so this is an O(n) operation
template <std::input_iterator Iterator>
auto customDistance(Iterator begin, Iterator end) {
   std::cout << "Called customDistance with input iterators\n";
   std::ptrdiff_t count{0};

   // increment from begin to end and count number of iterations
   for (auto& iter{begin}; iter != end; ++iter) {
      ++count;
   }

   return count;
}

// calculate the distance (number of items) between two iterators 
// using random-access iterators and an O(1) operation
template <std::random_access_iterator Iterator>
auto customDistance(Iterator begin, Iterator end) {
   std::cout << "Called customDistance with random-access iterators\n";
   return end - begin; // returns a std::ptrdiff_t value
}

int main() {
   std::array ints1{1, 2, 3, 4, 5}; // has random-access iterators
   std::list ints2{1, 2, 3}; // has bidirectional iterators

   auto result1{customDistance(ints1.begin(), ints1.end())};
   std::cout << "ints1 number of elements: " << result1 << "\n";
   auto result2{customDistance(ints2.begin(), ints2.end())};
   std::cout << "ints2 number of elements: " << result2 << "\n";
}


/**************************************************************************
 * (C) Copyright 1992-2022 by Deitel & Associates, Inc. and               *
 * Pearson Education, Inc. All Rights Reserved.                           *
 *                                                                        *
 * DISCLAIMER: The authors and publisher of this book have used their     *
 * best efforts in preparing the book. These efforts include the          *
 * development, research, and testing of the theories and programs        *
 * to determine their effectiveness. The authors and publisher make       *
 * no warranty of any kind, expressed or implied, with regard to these    *
 * programs or to the documentation contained in these books. The authors *
 * and publisher shall not be liable in any event for incidental or       *
 * consequential damages in connection with, or arising out of, the       *
 * furnishing, performance, or use of these programs.                     *
 **************************************************************************/