std::ranges:: views::adjacent_transform, std::ranges::adjacent_transform_view, std::ranges:: views::
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>
&&
|
(1) | (since C++23) |
namespace views {
template
<
std::size_t N >
|
(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 */ |
(since C++23) | |
template
<
class F >
constexpr /*range adaptor closure*/ adjacent_transform<N> ( F&& fun ) ; |
(since C++23) | |
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
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.
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)) modelsforward_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)
F
is also 2 and fun
adjacent_transform_view
always models forward_range
, and models bidirectional_range
, random_access_range
, or sized_range
, if adapted view
Member functions
constructs a adjacent_transform_view (public member function) |
|
returns an iterator to the beginning (public member function) |
|
returns an iterator or a sentinel to the end (public member function) |
|
returns the number of elements. Provided only if the underlying (adapted) range satisfies sized_range . (public member function) |
|
Inherited from std::ranges::view_interface |
|
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> ) |
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> )
|
|
returns the first element in the derived view. Provided if it satisfies forward_range . (public member function of std::ranges::view_interface<D> )
|
|
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> )
|
|
returns the n
th 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)
|
|
inner_sentinel (private)
|
|
Data members
Member name | Definition |
fun_ (private)
|
/*movable-box*/<F>
(exposition-only member object* |
inner_ (private)
|
ranges::adjacent_view<V,N>
(exposition-only member object* |
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* |
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
#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> | made rejected |
References
- C++23 standard (ISO/IEC 14882:2024):
- 26.7.27 Adjacent transform view [range.adjacent.transform]
See also
a view consisting of tuples of references to adjacent elements of the adapted view(class template) (range adaptor object) |
|
a view of a sequence that applies a transformation function to each element(class template) (range adaptor object) |
|
a view consisting 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 (algorithm function object) |