std::ranges::views::all, std::ranges::views::all_t
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C++
Feature test macros (C++20)
Concepts library (C++20)
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Ranges library
(C++23)(C++23)
(C++23)(C++23)
views::all_tviews::all
(C++23)(C++23)
(C++26)(C++26)
(C++23)(C++23)
(C++23)(C++23)
(C++23)(C++23)
(C++23)(C++23)
(C++23)(C++23)
(C++23)
(C++23)(C++23)
(C++23)
(C++23)(C++23)
(C++23)(C++23)
(C++23)(C++23)
(C++23)(C++23)
(C++23)(C++23)
(C++23)
Defined in header
<ranges>
inline constexpr /* unspecified */ all = /* unspecified */;
(1)
(since C++20)
template< ranges::viewable_range R >
using all_t = decltype(views::all(std::declval <R>()));
(2)
(since C++20)
using all_t = decltype(views::all(std::declval <R>()));
1) A RangeAdaptorObject (also a RangeAdaptorClosureObject) that returns a
view that includes all elements of its range argument. Given an expression e of type
R, the expression views::all(e) is expression-equivalent to:
- If std::decay_t <R> models
view, implicitly converting e to a std::decay_t <R> prvalue. - Otherwise, std::ranges::ref_view {e} if that expression is well-formed.
- Otherwise, std::ranges::owning_view {e}.
[edit] Example
Run this code
#include <iostream> #include <ranges> #include <type_traits> #include <vector> int main() { std::vector <int> v{0, 1, 2, 3, 4, 5}; for (int n : std::views::all(v) | std::views::take (2)) std::cout << n << ' '; std::cout << '\n'; static_assert(std::is_same < decltype(std::views::single (42)), std::ranges::single_view <int> >{}); static_assert(std::is_same < decltype(std::views::all(v)), std::ranges::ref_view <std::vector <int, std::allocator <int>>> >{}); int a[]{1, 2, 3, 4}; static_assert(std::is_same < decltype(std::views::all(a)), std::ranges::ref_view <int[4]> >{}); static_assert(std::is_same < decltype(std::ranges::subrange {std::begin (a) + 1, std::end (a) - 1}), std::ranges::subrange <int*, int*, std::ranges::subrange_kind (1)> >{}); }
Output:
0 1
[edit] Defect reports
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
| DR | Applied to | Behavior as published | Correct behavior |
|---|---|---|---|
| LWG 3724 | C++20 | views::all might result in hard error for some move-only views
|
it gets well-constrained |
| P2415R2 | C++20 | views::all returned a subrange for a non-view rvalue range
|
returns an owning_view for it
|