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

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 >
    inline 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 ith 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:
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.

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

(C++23)
 constructs a adjacent_transform_view
(public member function)
(C++23)
 returns an iterator to the beginning
(public member function)
(C++23)
 returns an iterator or a sentinel to the end
(public member function)
(C++23)
 returns the number of elements. Provided only if the underlying (adapted) range satisfies sized_range.
(public member function)
Inherited from std::ranges::view_interface
(C++20)
 returns whether the derived view is empty. Provided if it satisfies sized_range or forward_range.
(public member function of std::ranges::view_interface<D>)
(C++23)
 returns a constant iterator to the beginning of the range.
(public member function of std::ranges::view_interface<D>)
(C++23)
 returns a sentinel for the constant iterator of the range.
(public member function of std::ranges::view_interface<D>)
(C++20)
 returns whether the derived view is not empty. Provided if ranges::empty is applicable to it.
(public member function of std::ranges::view_interface<D>)
(C++20)
 returns the first element in the derived view. Provided if it satisfies forward_range.
(public member function of std::ranges::view_interface<D>)
(C++20)
 returns the last element in the derived view. Provided if it satisfies bidirectional_range and common_range.
(public member function of std::ranges::view_interface<D>)
(C++20)
 returns the nth element in the derived view. Provided if it satisfies random_access_range.
(public member function of std::ranges::view_interface<D>)

Deduction guides

(none)

Member types

Member type Definition
InnerView (private) ranges::adjacent_view<V, N>.
(exposition-only member type*)
inner_iterator (private)


(exposition-only member type*)
inner_sentinel (private)


(exposition-only member type*)

Data members

Member object Definition
fun_ (private) /*movable-box*/<F>
(exposition-only member object*)
inner_ (private) ranges::adjacent_view<V,N>
(exposition-only member object*)

Nested classes

(C++23)
 the iterator type
(exposition-only member class template*)
(C++23)
 the sentinel type used when adjacent_transform_view is not a common_range
(exposition-only member class template*)

Notes

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

std::ranges::zip_transform_view,
std::ranges::adjacent_view,
std::ranges::adjacent_transform_view

Example

#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

References

  • C++23 standard (ISO/IEC 14882:2023):
    • 26.7.27 Adjacent transform view [range.adjacent.transform]

See also

(C++23)
 a view consisting of tuples of references to adjacent elements of the adapted view
(class template) (range adaptor object)
(C++20)
 a view of a sequence that applies a transformation function to each element
(class template) (range adaptor object)
(C++23)
 a view consisting of tuples of results of application of a transformation function to corresponding elements of the adapted views
(class template) (customization point object)
(C++20)
 applies a function to a range of elements
(niebloid)

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