std::ranges::views::chunk_by, std::ranges::chunk_by_view
From cppreference.com
Defined in header <ranges>
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template< ranges::forward_range V, std::indirect_binary_predicate<iterator_t<V>, ranges::iterator_t<V>> Pred > |
(1) | (since C++23) |
namespace views { inline constexpr /* unspecified */ chunk_by = /* unspecified */ ; |
(2) | (since C++23) |
Call signature |
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template< ranges::viewable_range R, class Pred > requires /* see below */ |
(since C++23) | |
template< class Pred > constexpr /*range adaptor closure*/ chunk_by( Pred&& pred ); |
(since C++23) | |
1)
chunk_by_view
is a range adaptor that takes a view
and an invocable object pred (the binary predicate), and produces a view
of subranges (chunks), by splitting the underlying view between each pair of adjacent elements for which pred returns false. The first element of each such pair belongs to the previous chunk, and the second element belongs to the next chunk.2) The name views::chunk_by denotes a RangeAdaptorObject. Given a subexpression e and f, the expression views::chunk_by(e, f) is expression-equivalent to chunk_by_view(e, f).
chunk_by_view
always models forward_range
, and models bidirectional_range
and/or common_range
, if adapted view
type models the corresponding concepts.
chunk_by_view
never models borrowed_range
or sized_range
.
Contents |
[edit] Data members
Member | Definition |
V base_
|
the underlying view (exposition-only member object*) |
movable-box<Pred> pred_
|
an object that wraps the predicate used to split the elements of base_ (exposition-only member object*) |
non-propagating-cache <iterator> begin_
|
an object that caches the iterator to the first element (exposition-only member object*) |
[edit] Member functions
constructs a chunk_by_view (public member function) | |
returns a copy of the underlying (adapted) view (public member function) | |
returns a reference to the stored predicate (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 an iterator to the begin of the next subrange (exposition-only member function*) | |
returns an iterator to the begin of the previous subrange (exposition-only 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> )
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(C++23) |
returns a sentinel for the constant iterator of the range. (public member function of std::ranges::view_interface<D> )
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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> )
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returns the first element in the derived view. Provided if it satisfies forward_range . (public member function of std::ranges::view_interface<D> )
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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> )
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[edit] Deduction guides
[edit] Nested classes
the iterator type (exposition-only member class template*) |
[edit] Notes
In order to provide the amortized constant time complexity required by the range
concept, the result of begin()
is cached within the chunk_by_view
object. If the underlying range is modified after the first call to begin()
, subsequent uses of the chunk_by_view
object might have unintuitive behavior.
Feature-test macro | Value | Std | Feature |
---|---|---|---|
__cpp_lib_ranges_chunk_by |
202202L |
(C++23) | std::ranges::chunk_by_view
|
[edit] Example
Run this code
#include <functional> #include <iostream> #include <ranges> #include <string_view> void print_chunks(auto view, std::string_view separator = ", ") { for (auto const subrange : view) { std::cout << '['; for (std::string_view prefix; auto const& elem : subrange) std::cout << prefix << elem, prefix = separator; std::cout << "] "; } std::cout << '\n'; } int main() { std::initializer_list v1 = {1, 2, 3, 1, 2, 3, 3, 3, 1, 2, 3}; auto fn1 = std::ranges::less{}; auto view1 = v1 | std::views::chunk_by(fn1); print_chunks(view1); std::initializer_list v2 = {1, 2, 3, 4, 4, 0, 2, 3, 3, 3, 2, 1}; auto fn2 = std::ranges::not_equal_to{}; auto view2 = v2 | std::views::chunk_by(fn2); print_chunks(view2); std::string_view v3 = "__cpp_lib_ranges_chunk_by"; auto fn3 = [](auto x, auto y) { return not(x == '_' or y == '_'); }; auto view3 = v3 | std::views::chunk_by(fn3); print_chunks(view3, ""); std::string_view v4 = "\u007a\u00df\u6c34\u{1f34c}"; // "zß水🍌" auto fn4 = [](auto, auto ß) { return 128 == ((128 + 64) & ß); }; auto view4 = v4 | std::views::chunk_by(fn4); print_chunks(view4, ""); }
Output:
[1, 2, 3] [1, 2, 3] [3] [3] [1, 2, 3] [1, 2, 3, 4] [4, 0, 2, 3] [3] [3, 2, 1] [_] [_] [cpp] [_] [lib] [_] [ranges] [_] [chunk] [_] [by] [z] [ß] [水] [🍌]
[edit] References
- C++23 standard (ISO/IEC 14882:2024):
- 26.7.30 Chunk by view [range.chunk.by]
[edit] See also
a range of view s that are N -sized non-overlapping successive chunks of the elements of another view (class template) (range adaptor object) | |
a view whose Mth element is a view over the Mth through (M + N - 1)th elements of another view (class template) (range adaptor object) | |
a view consisting of elements of another view , advancing over N elements at a time(class template) (range adaptor object) |