std::ranges::take_view<V>::reserve_hint

 

C++

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Feature test macros (C++20)

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Concepts library (C++20)

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Metaprogramming library (C++11)

General utilities library

Containers library

Iterators library

Ranges library (C++20)

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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

 

std::ranges::take_view

Member functions

take_view::take_view

take_view::base

take_view::begin

take_view::end

take_view::size

take_view::reserve_hint (C++26)

Deduction guides

Sentinel

Member functions

take_view::sentinel::sentinel

Non-member functions

take_view::sentinel::base

operator==(std::counted_iterator,take_view::sentinel)

 

constexpr auto reserve_hint()	(1)	(since C++26)
constexpr auto reserve_hint() const	(2)	(since C++26)

Let W be V for overload (1) or const V for overload (2). Equivalent to

if constexpr (ranges::approximately_sized_range<W>)
{
    auto n = static_cast<ranges::range_difference_t<W>>(ranges::reserve_hint(base_));
    return to-unsigned-like(ranges::min(n, count_));
}
return to-unsigned-like(count_);

Return value

The approximate size of the resulting range.

Notes

Feature-test macro	Value	Std	Feature
__cpp_lib_ranges_reserve_hint	202502L	(C++26)	ranges::approximately_sized_range and reserve_hint (1,2)

See also

size	returns the number of elements, provided only if the underlying (adapted) range satisfies sized_range (public member function)