std::ranges::views::lazy_split, std::ranges::lazy_split_view
<ranges>
requires ranges::view <V> &&
ranges::view <Pattern> &&
std::indirectly_comparable <ranges::iterator_t <V>,
ranges::iterator_t <Pattern>,
ranges::equal_to > &&
(ranges::forward_range <V> || /*tiny-range*/<Pattern>)
class lazy_split_view
inline constexpr /* unspecified */ lazy_split = /* unspecified */;
requires /* see below */
constexpr /* range adaptor closure */ lazy_split( Pattern&& pattern );
concept /*tiny-range*/ =
ranges::sized_range <R> &&
requires { /* is-statically-constexpr-sized */<R>; } &&
lazy_split_view takes a view and a delimiter, and splits the view into subranges on the delimiter.
Two major scenarios are supported:
- The view is an
input_range, the delimiter is a single element (wrapped in asingle_view). - The view is a
forward_range, the delimiter is aviewof elements.
Pattern satisfies sized_range, Pattern::size() is a constant expression and suitable as a template constant argument, and the value of Pattern::size() is less than or equal to 1. Notably, empty_view and single_view satisfy this concept.lazy_split_view models the concepts forward_range and input_range when the underlying view V models respective concepts, and models common_range when V models both forward_range and common_range.
The inner range (ranges::range_reference_t <lazy_split_view>) models the concepts forward_range and input_range when the underlying view V models respective concepts. It does not model common_range, and cannot be used with algorithms that expect a bidirectional_range or higher.
Unlike split_view, lazy_split_view does not maintain the continuity of the subrange.
Contents
[edit] Data members
Pattern pattern_ (private)
the pattern that is used as a delimiter to split the underlying view (exposition-only member object*)
current_ (private) (present only if
V does not satisfy forward_range)
an object that caches the result of calls to begin() (exposition-only member object*)
[edit] Member functions
Inherited from std::ranges::view_interface
sized_range or forward_range (public member function of
std::ranges::view_interface<D>) [edit]
(public member function of
std::ranges::view_interface<D>) [edit]
(public member function of
std::ranges::view_interface<D>) [edit]
(public member function of
std::ranges::view_interface<D>) [edit]
forward_range (public member function of
std::ranges::view_interface<D>) [edit]
[edit] Nested classes
[edit] Deduction guides
[edit] Notes
The name lazy_split_view is introduced by the post-C++20 defect report P2210R2. It has the same lazy mechanism as that of the old split_view before change.
[edit] Example
#include <algorithm> #include <iostream> #include <ranges> #include <string_view> auto print = [](auto const& view) { // `view` is of std::views::lazy_split_view::__outer_iterator::value_type for (std::cout << "{ "; const auto element : view) std::cout << element << ' '; std::cout << "} "; }; int main() { constexpr static auto source = {0, 1, 0, 2, 3, 0, 4, 5, 6, 0, 7, 8, 9}; constexpr int delimiter{0}; constexpr std::ranges::lazy_split_view outer_view{source, delimiter}; std::cout << "splits[" << std::ranges::distance (outer_view) << "]: "; for (auto const& inner_view: outer_view) print(inner_view); constexpr std::string_view hello{"Hello C++ 20 !"}; std::cout << "\n" "substrings: "; std::ranges::for_each (hello | std::views::lazy_split(' '), print); constexpr std::string_view text{"Hello-+-C++-+-20-+-!"}; constexpr std::string_view delim{"-+-"}; std::cout << "\n" "substrings: "; std::ranges::for_each (text | std::views::lazy_split(delim), print); }
Output:
splits[5]: { } { 1 } { 2 3 } { 4 5 6 } { 7 8 9 }
substrings: { H e l l o } { C + + } { 2 0 } { ! }
substrings: { H e l l o } { C + + } { 2 0 } { ! }[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 |
|---|---|---|---|
| P2210R2 | C++20 | the old split_view was too lazy to be easily used
|
moves its functionality to lazy_split_view
|
[edit] See also
view over the subranges obtained from splitting another view using a delimiter(class template) (range adaptor object)[edit]