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

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< cpp‎ | ranges
 
 
Ranges library
Range access
Range conversions
(C++23)

Range primitives



Dangling iterator handling
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(until 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)
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:
2) Calculates the suitable view type of a viewable_range type.

[edit] Example

#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

[edit] See also

an empty view with no elements
(class template) (variable template)[edit]
a view that contains a single element of a specified value
(class template) (customization point object)[edit]
a view with unique ownership of some range
(class template) [edit]