ranges/filterview.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 <string>
#include <vector>
#include <ranges>

void print(std::ranges::input_range auto&& coll)
{
  for (const auto& elem : coll) {
    std::cout << elem << ' ';
  }
  std::cout << '\n';
}

int main()
{
  std::vector coll{1, 2, 3, 4, 1, 2, 3, 4, 1};

  print(coll);                                   // 1 2 3 4 1 2 3 4 1
  auto less4 = [] (auto v) { return v < 4; };
  print(std::ranges::filter_view{coll, less4});  // 1 2 3 1 2 3 1
  print(coll | std::views::filter(less4));       // 1 2 3 1 2 3 1
}