std::ranges::views::join, std::ranges::join_view - cppreference.com (original) (raw)

1. A range adaptor that represents view consisting of the sequence obtained from flattening a view of ranges.

join_view models input_range.

join_view models forward_range when:

• ranges::range_reference_t<V> is a reference type, and
• V and ranges::range_reference_t<V> each model forward_range.

join_view models bidirectional_range when:

• ranges::range_reference_t<V> is a reference type,
• V models bidirectional_range, and
• ranges::range_reference_t<V> models both bidirectional_range and common_range.

join_view models common_range when:

• ranges::range_reference_t<V> is a reference type, and
• V and ranges::range_reference_t<V> each model forward_range and common_range.

Contents

• 1 Member functions
  • 1.1 Inherited from std::ranges::view_interface
• 2 Deduction guides
• 3 Nested classes
• 4 Notes
• 5 Example
• 6 Defect reports
• 7 See also

[edit] Member functions

[edit] Deduction guides

[edit] Nested classes

| | the iterator type(exposition-only member class template*) | | ------------------------------------------------------------- | | | the sentinel type(exposition-only member class template*) |

[edit] Notes

Before P2328R1 was adopted, the inner range type (ranges::range_reference_t<V>) cannot be a container type (but can be reference to container). For example, it was not allowed to join a transform_view of std::string prvalue.

struct Person { int age; std::string name; };   auto f(std::vector& v) { // return v | std::views::transform([](auto& p){ return p.name; }) // | std::views::join; // error before P2328R1 return v | std::views::transform([](auto& p) -> std::string& { return p.name; }) | std::views::join; // OK }

[edit] Example

#include #include #include #include   int main() { using namespace std::literals;   const auto bits = {"https:"sv, "//"sv, "cppreference"sv, "."sv, "com"sv}; for (char const c : bits | std::views::join) std::cout << c; std::cout << '\n';   const std::vector<std::vector> v{{1, 2}, {3, 4, 5}, {6}, {7, 8, 9}}; auto jv = std::ranges::join_view(v); for (int const e : jv) std::cout << e << ' '; std::cout << '\n'; }

Output:

https://cppreference.com 1 2 3 4 5 6 7 8 9

[edit] Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

[edit] See also