lazy_split_view
takes a
view
and a delimiter, and splits the
view
into subranges on the delimiter.
Two major scenarios are supported:
input_range, the delimiter is a single element (wrapped in a single_view).forward_range, the delimiter is a view of elements.The exposition-only concept
/*tiny-range*/<Pattern>is satisfied if
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.
V base_ (private) the underlying view
Pattern pattern_ (private) the pattern that is used as a delimiter to split the underlying view
current_ (private)
V does not satisfy forward_range) an object that caches the result of calls to begin()
lazy_split_view
sized_range or forward_range
std::ranges::view_interface<D>) [edit] returns a constant iterator to the beginning of the range
std::ranges::view_interface<D>) [edit] returns a sentinel for the constant iterator of the range
std::ranges::view_interface<D>) [edit] returns whether the derived view is not empty, provided only if ranges::empty is applicable to it
std::ranges::view_interface<D>) [edit] returns the first element in the derived view, provided if it satisfies forward_range
std::ranges::view_interface<D>) [edit] [edit] Nested classes the iterator type
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.
#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 oldsplit_view was too lazy to be easily used moves its functionality to lazy_split_view [edit] See also
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