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

 

C++

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Feature test macros(C++20)

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Concepts library(C++20)

Diagnostics library

Memory management library

Metaprogramming library(C++11)

General utilities library

Containers library

Iterators library

Ranges library(C++20)

Algorithms library

Strings library

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Numerics library

Date and time library

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Filesystem library(C++17)

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Technical specifications

Symbols index

External libraries

 

Ranges library

Range access begin cbegin   end cend rbegin crbegin   rend crend size ssize   data cdata reserve_hint (C++26)   empty

Range conversions std::from_range_t std::from_range (C++23)(C++23)     to (C++23)

Dangling iterator handling dangling borrowed_iterator_t borrowed_subrange_t

Range primitives
range_size_trange_difference_trange_value_t elements_of (C++23)	iterator_tconst_iterator_tsentinel_tconst_sentinel_t (C++23)(C++23)	range_reference_trange_const_reference_trange_rvalue_reference_trange_common_reference_t (C++23)

Range concepts
range borrowed_range    common_range	sized_range viewable_range    view	input_range output_range forward_range	bidirectional_range    random_access_range contiguous_range	approximately_sized_range (C++26) constant_range (C++23)

Views
view_interface	subrange

Range factories
empty_viewviews::empty	single_viewviews::single	basic_istream_viewviews::istream	iota_viewviews::iota	repeat_viewviews::repeat (C++23)(C++23)

Range adaptors
views::all_tviews::all as_rvalue_viewviews::as_rvalue (C++23)(C++23)   filter_viewviews::filter transform_viewviews::transform take_viewviews::take take_while_viewviews::take_while common_viewviews::common views::counted to_input_viewviews::to_input (C++26)(C++26)	ref_view drop_viewviews::drop drop_while_viewviews::drop_while lazy_split_viewviews::lazy_split split_viewviews::split join_viewviews::join join_with_viewviews::join_with (C++23)(C++23)   concat_viewviews::concat (C++26)(C++26) cache_latest_viewviews::cache_latest (C++26)(C++26)	owning_view 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 closure objects range_adaptor_closure (C++23)

Range adaptor objects

Helper items
copyable-box movable-box (until C++23)  (C++23)	simple-view non-propagating-cache

 

Defined in header <ranges>
inlineconstexpr/* 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 <<' ';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)