Function main

Exercises/Modules/Chapter 21/Soln21_02/Soln21_02.cpp:71–113

};

int main()
{
  std::vector<Box> boxes{ {2.0, 2.0, 3.0}, {1.0, 3.0, 2.0}, {1.0, 2.0, 1.0}, {2.0, 3.0, 3.0} };

  // Step 1: create a view where begin() and end() are different.
  // The result of the take_while() range adapter has this property
  // (or, at least, it should have as per its specification in the Standard).
  auto first_boxes{ boxes | take_while([](const Box& box) { return box.volume() < 15; }) };
  
  /* This therefore generally does not compile... */
  //std::cout << "Volume of smallest box: " 
  //  << original_find_optimum(first_boxes.begin(), first_boxes.end(),
  //        [](const Box& box1, const Box& box2) { return box1.isSmallerThan(box2); })->volume()
  //  << std::endl;

  // Side-note: you can use the std::ranges::views::common to turn a range
  // where begin and end have a different type into a view where they do.
  auto common_boxes{ first_boxes | common };
  std::cout << "Volume of smallest box: " 
    << original_find_optimum(common_boxes.begin(), common_boxes.end(),
          [](const Box& box1, const Box& box2) { return box1.isSmallerThan(box2); })->volume()
    << std::endl;
  
  // Step 2: Show off our shiny new, modernised version of find_optimum()
  // First off: no need for the common adapter!
  std::cout << "Volume of largest box: "
    << find_optimum(first_boxes.begin(), first_boxes.end(),
          [](const Box& box1, const Box& box2) { return !box1.isSmallerThan(box2); })->volume()
    << std::endl;

  // Other cool features of our modern find_optimum() version include projection 
  // and the support for member function pointers. So no more lambdas required here!

  // Use a member-function pointer for the comparison function
  std::cout << "Volume of smallest box: " 
    << find_optimum(first_boxes.begin(), first_boxes.end(), &Box::isSmallerThan)->volume() 
    << std::endl;

  // Use a member-function pointer for the new projection functionality
  std::cout << "Volume of largest box: " 
    << find_optimum(first_boxes.begin(), first_boxes.end(), std::greater<>{}, &Box::volume)->volume()
    << std::endl;
}