NAME¶

std::ranges::views::all,std::ranges::views::all_t - std::ranges::views::all,std::ranges::views::all_t

Synopsis¶

Defined in header <ranges>
inline constexpr /* unspecified */ all = /* unspecified */; (1) (since C++20)
template< ranges::viewable_range 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:
* Implicitly converting e to a std::decay_t<R> prvalue, if std::decay_t<R> models
view.
* Otherwise, std::ranges::ref_view{e} if that expression is well-formed.
* Otherwise, std::ranges::owning_view{e}.
2) Calculates the suitable view type of a viewable_range type.

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

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 it gets well-constrained
error for some move-only views
P2415R2 C++20 views::all returned a subrange for returns an owning_view for it
a non-view rvalue range

See also¶

ranges::empty_view an empty view with no elements
views::empty (class template) (variable template)
(C++20)
ranges::single_view a view that contains a single element of a specified value
views::single (class template) (customization point object)
(C++20)
ranges::owning_view a view with unique ownership of some range
(C++20) (class template)