std::ranges::views::adjacent_transform, std::ranges::adjacent_transform_view, std::ranges::views::pairwise_transform

 

C++

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Standard library headers

Named requirements

Feature test macros (C++20)

Language support library

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

Text processing library

Numerics library

Date and time library

Input/output library

Filesystem library (C++17)

Concurrency support library (C++11)

Execution control library (C++26)

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 as_input_viewviews::as_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::adjacent_transform_view

Member functions

adjacent_transform_view::adjacent_transform_view

adjacent_transform_view::begin

adjacent_transform_view::end

adjacent_transform_view::size

adjacent_transform_view::reserve_hint (C++26)

Iterator

Member functions

adjacent_transform_view::iterator::iterator

adjacent_transform_view::iterator::operator*

adjacent_transform_view::iterator::operator[]

adjacent_transform_view::iterator::operator++ adjacent_transform_view::iterator::operator++(int) adjacent_transform_view::iterator::operator-- adjacent_transform_view::iterator::operator--(int) adjacent_transform_view::iterator::operator+= adjacent_transform_view::iterator::operator-=

Non-member functions

operator==(adjacent_transform_view::iterator) operator<(adjacent_transform_view::iterator) operator>(adjacent_transform_view::iterator) operator<=(adjacent_transform_view::iterator) operator>=(adjacent_transform_view::iterator) operator<=>(adjacent_transform_view::iterator)

operator+(adjacent_transform_view::iterator) operator-(adjacent_transform_view::iterator)

Sentinel

Member functions

adjacent_transform_view::sentinel::sentinel

Non-member functions

operator==(adjacent_transform_view::iterator,adjacent_transform_view::sentinel)

operator-(adjacent_transform_view::iterator,adjacent_transform_view::sentinel)

 

Defined in header <ranges>
template< ranges::forward_range V, std::move_constructible F, std::size_t N > requires ranges::view<V> && (N > 0) && std::is_object_v<F> && std::regular_invocable<F&, /*REPEAT*/(ranges::range_reference_t<V>, N)...> && /*can-reference*/<std::invoke_result_t<F&, /*REPEAT*/(ranges::range_reference_t<V>, N)...>> class adjacent_transform_view : public ranges::view_interface<adjacent_transform_view<V, F, N>>	(1)	(since C++23)
namespace views { template< std::size_t N > constexpr /* unspecified */ adjacent_transform = /* unspecified */; }	(2)	(since C++23)
namespace views { inline constexpr auto pairwise_transform = adjacent_transform<2>; }	(3)	(since C++23)
Call signature
template< ranges::viewable_range R, class F > requires /* see below */ constexpr ranges::view auto adjacent_transform<N>( R&& r, F&& fun );		(since C++23)
template< class F > constexpr /*range adaptor closure*/ adjacent_transform<N>( F&& fun );		(since C++23)

1) adjacent_transform_view is a range adaptor that takes a view and an invocable object fun, and produces a view whose i^th element is a value that is the result of applying fun to each element in [i, i + N) of the original view. F always has arity N.

Let S be the size of the original view. Then the size of produced view is:

• S - N + 1, if S >= N,
• 0 otherwise, and the resulting view is empty.

2) The name views::adjacent_transform<N> denotes a RangeAdaptorObject. Given subexpressions e and f, and a constant expression N, the expression views::adjacent_transform<N>(e, f) is expression-equivalent to:

• ((void)e, views::zip_transform(f)), if N is equal to 0 and decltype((e)) models forward_range (except that the evaluations of e and f are indeterminately sequenced),
• adjacent_transform_view<views::all_t<decltype((e))>, std::decay_t<decltype((f))>, N>(e, f) otherwise.

3) The name views::pairwise_transform denotes a RangeAdaptorObject that behaves exactly as views::adjacent_transform<2>. In particular, the arity of F is also 2 and fun is a binary invocable object.

See More

adjacent_transform_view always models forward_range, and models bidirectional_range, random_access_range, or sized_range, if adapted view type models the corresponding concept.

Member functions

(constructor)	constructs a adjacent_transform_view (public member function)
begin	returns an iterator to the beginning (public member function)
end	returns an iterator or a sentinel to the end (public member function)
size	returns the number of elements, provided only if the underlying (adapted) range satisfies sized_range (public member function)
reserve_hint (C++26)	returns the approximate size of the resulting approximately_sized_range (public member function)
Inherited from ranges::view_interface
empty	returns whether the derived view is empty, provided only if it satisfies sized_range or forward_range (public member function of std::ranges::view_interface<D>)
cbegin (C++23)	returns a constant iterator to the beginning of the range (public member function of std::ranges::view_interface<D>)
cend (C++23)	returns a sentinel for the constant iterator of the range (public member function of std::ranges::view_interface<D>)
operator bool	returns whether the derived view is not empty, provided only if ranges::empty is applicable to it (public member function of std::ranges::view_interface<D>)
front	returns the first element in the derived view, provided if it satisfies forward_range (public member function of std::ranges::view_interface<D>)
back	returns the last element in the derived view, provided only if it satisfies bidirectional_range and common_range (public member function of std::ranges::view_interface<D>)
operator[]	returns the nth element in the derived view, provided only if it satisfies random_access_range (public member function of std::ranges::view_interface<D>)

Nested types

Type	Definition
InnerView (private)	ranges::adjacent_view<V, N> (exposition-only member type*)
inner_iterator (private)	ranges::iterator_t<const InnerView>, if Const is true. Otherwise, ranges::iterator_t<InnerView> (exposition-only member type*)
inner_sentinel (private)	ranges::sentinel_t<const InnerView>, if Const is true. Otherwise, ranges::sentinel_t<InnerView> (exposition-only member type*)

Data members

Member	Description
/*movable-box*/<F> fun_ (private)	the transforming invocable object (exposition-only member object*)
ranges::adjacent_view<V,N> inner_ (private)	the stored view (exposition-only member object*)

Nested classes

iterator	the iterator type (exposition-only member class template*)
sentinel	the sentinel type used when adjacent_transform_view is not a common_range (exposition-only member class template*)

Notes

views::adjacent_transform only accepts foward ranges even when N is 0.

Feature-test macro	Value	Std	Feature
__cpp_lib_ranges_zip	202110L	(C++23)	ranges::zip_view, ranges::zip_transform_view, ranges::adjacent_view, ranges::adjacent_transform_view

Example

Run this code

#include <array>
#include <iostream>
#include <ranges>

int main()
{
    constexpr static std::array data{1, 2, 3, 4, 5, 6};
    constexpr int window{3};

    auto Fun = [](auto... ints) { return (... + ints); };
    // Alternatively, the Fun could be any ternary (if window == 3) callable, e.g.:
    // auto Fun = [](int x, int y, int z) { return x + y + z; };

    constexpr auto view = data | std::views::adjacent_transform<window>(Fun);

    static_assert(
        view.size() == (data.size() - window + 1)
        && std::array{6, 9, 12, 15}
        == std::array{view[0], view[1], view[2], view[3]}
        && view[0] == Fun(data[0], data[1], data[2])
        && view[1] == Fun(data[1], data[2], data[3])
        && view[2] == Fun(data[2], data[3], data[4])
        && view[3] == Fun(data[3], data[4], data[5])
    );

    for (int x : view)
        std::cout << x << ' ';
    std::cout << '\n';
}

Output:

6 9 12 15

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 4098	C++23	views::adjacent_transform<0> used to accept input-only ranges	made rejected

References

• C++23 standard (ISO/IEC 14882:2024):

• 26.7.27 Adjacent transform view [range.adjacent.transform]

See also

ranges::adjacent_viewviews::adjacent (C++23)	a view consisting of tuples of references to adjacent elements of the adapted view (class template) (range adaptor object)
ranges::transform_viewviews::transform (C++20)	a view of a sequence that applies a transformation function to each element (class template) (range adaptor object)
ranges::zip_transform_viewviews::zip_transform (C++23)	a view consisting of results of application of a transformation function to corresponding elements of the adapted views (class template) (customization point object)
ranges::transform (C++20)	applies a function to a range of elements (algorithm function object)