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

 

C++

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Ranges library (C++20)

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Technical specifications

Symbols index

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Ranges library

Range access
begin cbegin end cend	rbegin crbegin rend crend	size ssize data cdata	empty
Range conversions
to (C++23)
Range primitives
range_size_trange_difference_trange_value_trange_reference_t	iterator_tconst_iterator_tsentinel_tconst_sentinel_t (C++23)(C++23)	range_const_reference_trange_rvalue_reference_trange_common_reference_t (C++23)	elements_of (C++23)
Dangling iterator handling
dangling	borrowed_iterator_t	borrowed_subrange_t
Range concepts
range borrowed_range sized_range constant_range (C++23)	common_range view viewable_range	input_range output_range forward_range	bidirectional_range random_access_range contiguous_range
Views
view_interface	subrange
Range factories
empty_viewviews::empty single_viewviews::single	iota_viewviews::iota repeat_viewviews::repeat (C++23)(C++23)	basic_istream_viewviews::istream
Range adaptors
views::all_tviews::all ref_view owning_view as_rvalue_viewviews::as_rvalue (C++23)(C++23) filter_viewviews::filter transform_viewviews::transform take_viewviews::take take_while_viewviews::take_while	drop_viewviews::drop drop_while_viewviews::drop_while join_viewviews::join join_with_viewviews::join_with (C++23)(C++23) lazy_split_viewviews::lazy_split split_viewviews::split views::counted common_viewviews::common	reverse_viewviews::reverse as_const_viewviews::as_const (C++23)(C++23) elements_viewviews::elements keys_viewviews::keys values_viewviews::values enumerate_viewviews::enumerate (C++23)(C++23) zip_viewviews::zip (C++23)(C++23) zip_transform_viewviews::zip_transform (C++23)(C++23)	adjacent_viewviews::adjacent (C++23)(C++23) views::pairwise (C++23) adjacent_transform_viewviews::adjacent_transform (C++23)(C++23) views::pairwise_transform (C++23) chunk_viewviews::chunk (C++23)(C++23) slide_viewviews::slide (C++23)(C++23) chunk_by_viewviews::chunk_by (C++23)(C++23) stride_viewviews::stride (C++23)(C++23) cartesian_product_viewviews::cartesian_product (C++23)(C++23)
Range generators
std::generator (C++23)
Range adaptor objects
Range adaptor closure objects
range_adaptor_closure (C++23)
Helper items
copyable-box movable-box (until C++23)(C++23)	simple-view non-propagating-cache

 

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:

• 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 << ' ';
 
    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 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

See also

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