std::ranges::views::adjacent_transform, std::ranges::adjacent_transform_view, std::ranges::views::pairwise_transform - cppreference.com (original) (raw)

std::ranges::adjacent_transform_view

Defined in header
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:

  1. 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.

Contents

[edit] Member functions

(constructor) constructs a adjacent_transform_view (public member function) [edit]
begin returns an iterator to the beginning (public member function) [edit]
end returns an iterator or a sentinel to the end (public member function) [edit]
size returns the number of elements, provided only if the underlying (adapted) range satisfies sized_range (public member function) [edit]
reserve_hint(C++26) returns the approximate size of the resulting approximately_sized_range (public member function) [edit]
Inherited from std::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) [edit]
cbegin(C++23) returns a constant iterator to the beginning of the range (public member function of std::ranges::view_interface) [edit]
cend(C++23) returns a sentinel for the constant iterator of the range (public member function of std::ranges::view_interface) [edit]
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) [edit]
front returns the first element in the derived view, provided if it satisfies forward_range (public member function of std::ranges::view_interface) [edit]
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) [edit]
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) [edit]

[edit] Nested types

[edit] 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*)

[edit] Nested classes

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

[edit] 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

[edit] Example

#include #include #include   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(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:

[edit] 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

[edit] References

[edit] See also