ranges/sentinel3.cpp

The following code example is taken from the book
C++20 - The Complete Guide by Nicolai M. Josuttis, Leanpub, 2021
The code is licensed under a Creative Commons Attribution 4.0 International License.

---

// raw code

#include <iostream>
#include <algorithm>

template<auto End>
struct EndValue {
  bool operator== (auto pos) const {
    return *pos == End;  // end is where iterator points to End
  }
};

int main()
{
  std::vector coll = {42, 8, 0, 15, 7, -1};

  // define a range referring to coll with the value 7 as end:
  std::ranges::subrange range{coll.begin(), EndValue<7>{}};

  // sort the elements of this range:
  std::ranges::sort(range);

  // print the elements of the range:
  std::ranges::for_each(range,
                        [] (auto val) {
                          std::cout << ' ' << val;
                        });
  std::cout << '\n';

  // print all elements of coll up to -1:
  std::ranges::for_each(coll.begin(), EndValue<-1>{},
                        [] (auto val) {
                          std::cout << ' ' << val;
                        });
  std::cout << '\n';
}