NAME¶

std::ranges::views::adjacent_transform,std::ranges::adjacent_transform_view, - std::ranges::views::adjacent_transform,std::ranges::adjacent_transform_view,

Synopsis¶

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&, (since
/*REPEAT*/(ranges::range_reference_t<V>, N)...> && (1) C++23)
/*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>>
namespace views {

template< std::size_t N > (since
inline constexpr /* unspecified */ adjacent_transform = /* (2) C++23)
unspecified */;

}
namespace views {
(since
inline constexpr auto pairwise_transform = adjacent_transform<2>; (3) C++23)

}
Call signature
template< ranges::viewable_range R, class F >
(since
requires /* see below */ C++23)

constexpr ranges::view auto adjacent_transform<N>( R&& r, F&& fun );
template< class F > (since
constexpr /*range adaptor closure*/ adjacent_transform<N>( F&& fun ); 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 (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.

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
(C++23) (public member function)
begin returns an iterator to the beginning
(C++23) (public member function)
end returns an iterator or a sentinel to the end
(C++23) (public member function)
size returns the number of elements. Provided only if the underlying
(C++23) (adapted) range satisfies sized_range.
(public member function)
Inherited from std::ranges::view_interface
empty returns whether the derived view is empty. Provided if it satisfies
(C++20) sized_range or forward_range.
(public member function of std::ranges::view_interface<D>)
cbegin returns a constant iterator to the beginning of the range.
(C++23) (public member function of std::ranges::view_interface<D>)
cend returns a sentinel for the constant iterator of the range.
(C++23) (public member function of std::ranges::view_interface<D>)
operator bool returns whether the derived view is not empty. Provided if
(C++20) 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
(C++20) satisfies forward_range.
(public member function of std::ranges::view_interface<D>)
back returns the last element in the derived view. Provided if it satisfies
(C++20) bidirectional_range and common_range.
(public member function of std::ranges::view_interface<D>)
operator[] returns the n^th element in the derived view. Provided if it satisfies
(C++20) 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*)
* ranges::iterator_t<const InnerView>, if Const is true.
inner_iterator (private) Otherwise,
* ranges::iterator_t<InnerView>.
(exposition-only member type*)
* ranges::sentinel_t<const InnerView>, if Const is true.
inner_sentinel (private) Otherwise,
* ranges::sentinel_t<InnerView>.
(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

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

Notes¶

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

References¶

* C++23 standard (ISO/IEC 14882:2023):

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

See also¶

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