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 <vector>
#include <list>
#include <ranges>
void print(auto&& coll)
{
for (const auto& elem : coll) {
std::cout << elem << ' ';
}
std::cout << '\n';
}
int main()
{
std::vector vec{1, 2, 3, 4};
std::list lst{1, 2, 3, 4};
auto biggerThan2 = [](auto v){
return v > 2;
};
auto vVec = vec | std::views::filter(biggerThan2);
auto vLst = lst | std::views::filter(biggerThan2);
// insert a new element at the front (=> 0 1 2 3 4)
vec.insert(vec.begin(), 0);
lst.insert(lst.begin(), 0);
print(vVec); // OK: 3 4
print(vLst); // OK: 3 4
// insert more elements at the front (=> 98 99 0 -1 0 1 2 3 4)
vec.insert(vec.begin(), {98, 99, 0, -1});
lst.insert(lst.begin(), {98, 99, 0, -1});
print(vVec); // OOPS: -1 3 4
print(vLst); // OOPS: 3 4
// creating a copy heals (except with random access):
auto vVec2 = vVec;
auto vLst2 = vLst;
print(vVec2); // OOPS: -1 3 4
print(vLst2); // OK: 98 99 3 4
}