std::ranges::take_while_view 无法管道

Question

auto int_v10 = std::vector{8,7,3};
//fail    auto rng2 = int_v10 | std::ranges::take_while_view([](int x) {return x> 5;} ) | std::ranges::views::common;
auto rng2 = int_v10 | std::ranges::views::take_while([](int x) {return x> 5;} ) | std::ranges::views::common;
auto result4 = std::accumulate(rng2.begin(), rng2.end(),0);

std::cout<<"Result4: "<<result4<<'\n';

https://en.cppreference.com/w/cpp/ranges/take_while_view
为什么 std::ranges::take_while_view 结果无法通过管道传递到下一个代码块。 std::ranges::views::take_while 可以吗？

Answer 1

take_while_view has only two constructors:

take_while_view() = default;
constexpr take_while_view(V base, Pred pred);

第二个构造函数需要接受两个参数，一个是base，一个是pred，所以需要这样构造：

auto rng2 = std::ranges::take_while_view(int_v10, [](int x) {return x > 5;}) 
          | std::ranges::views::common;

std::ranges::take_while_view 无法管道

std::ranges::take_while_view cannot pipe

c++

std-ranges