std::ranges::views::lazy_split, std::ranges::lazy_split_view

 

C++

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Standard library

Standard library headers

Named requirements

Feature test macros (C++20)

Language support library

Concepts library (C++20)

Metaprogramming library (C++11)

Diagnostics library

General utilities library

Strings library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Numerics library

Localizations library

Input/output library

Filesystem library (C++17)

Regular expressions library (C++11)

Concurrency support library (C++11)

Technical specifications

Symbols index

External libraries

 

Ranges library

Range access
begin cbegin end cend	rbegin crbegin rend crend	size ssize data cdata	empty
Range conversions
to (C++23)
Range primitives
range_size_trange_difference_trange_value_trange_reference_t	iterator_tconst_iterator_tsentinel_tconst_sentinel_t (C++23)(C++23)	range_const_reference_trange_rvalue_reference_trange_common_reference_t (C++23)	elements_of (C++23)
Dangling iterator handling
dangling	borrowed_iterator_t	borrowed_subrange_t
Range concepts
range borrowed_range sized_range constant_range (C++23)	common_range view viewable_range	input_range output_range forward_range	bidirectional_range random_access_range contiguous_range
Views
view_interface	subrange
Range factories
empty_viewviews::empty single_viewviews::single	iota_viewviews::iota repeat_viewviews::repeat (C++23)(C++23)	basic_istream_viewviews::istream
Range adaptors
views::all_tviews::all ref_view owning_view as_rvalue_viewviews::as_rvalue (C++23)(C++23) filter_viewviews::filter transform_viewviews::transform take_viewviews::take take_while_viewviews::take_while	drop_viewviews::drop drop_while_viewviews::drop_while join_viewviews::join join_with_viewviews::join_with (C++23)(C++23) lazy_split_viewviews::lazy_split split_viewviews::split views::counted common_viewviews::common	reverse_viewviews::reverse as_const_viewviews::as_const (C++23)(C++23) elements_viewviews::elements keys_viewviews::keys values_viewviews::values enumerate_viewviews::enumerate (C++23)(C++23) zip_viewviews::zip (C++23)(C++23) zip_transform_viewviews::zip_transform (C++23)(C++23)	adjacent_viewviews::adjacent (C++23)(C++23) views::pairwise (C++23) adjacent_transform_viewviews::adjacent_transform (C++23)(C++23) views::pairwise_transform (C++23) chunk_viewviews::chunk (C++23)(C++23) slide_viewviews::slide (C++23)(C++23) chunk_by_viewviews::chunk_by (C++23)(C++23) stride_viewviews::stride (C++23)(C++23) cartesian_product_viewviews::cartesian_product (C++23)(C++23)
Range generators
std::generator (C++23)
Range adaptor objects
Range adaptor closure objects
range_adaptor_closure (C++23)
Helper items
copyable-box movable-box (until C++23)(C++23)	simple-view non-propagating-cache

 

std::ranges::lazy_split_view

Member functions

lazy_split_view::lazy_split_view (C++20)

lazy_split_view::base (C++20)

lazy_split_view::begin (C++20)

lazy_split_view::end (C++20)

Nested classes

lazy_split_view::outer_iterator (C++20)

lazy_split_view::outer_iterator::value_type (C++20)

lazy_split_view::inner_iterator (C++20)

Deduction guides

 

Defined in header <ranges>
template< ranges::input_range V, ranges::forward_range Pattern > 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 :     public ranges::view_interface<lazy_split_view<V, Pattern>>	(1)	(since C++20)
namespace views {     inline constexpr /* unspecified */ lazy_split = /* unspecified */; }	(2)	(since C++20)
Call signature
template< ranges::viewable_range R, class Pattern >     requires /* see below */ constexpr ranges::view auto lazy_split( R&& r, Pattern&& pattern );		(since C++20)
template< class Pattern > constexpr /* range adaptor closure */ lazy_split( Pattern&& pattern );		(since C++20)
Helper concepts
template< class R > concept /* tiny-range */ =     ranges::sized_range<R> &&     requires { /* is-statically-constexpr-sized */<R>; } &&     (std::remove_reference_t<R>::size() <= 1);	(3)	(exposition only*)

1) 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 a single_view).
• The view is a forward_range, the delimiter is a view of elements.

2) A RangeAdaptorObject. The expression views::lazy_split(e, f) is expression-equivalent to lazy_split_view(e, f).

3) 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 non-type 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.

Data members

Typical implementations of lazy_split_view hold two or three non-static data members:

• the underlying view of type V (shown here as base_ for exposition only),
• the pattern (shown here as pattern_ for exposition only) that is used as a delimiter to split the underlying view, and
• the caching object (shown here as current_ for exposition only) of the std::optional-like exposition-only type /* non-propagating-cache */<ranges::iterator_t<V>>. The current_ caches the result of calls to begin(). Present only if V does not satisfy forward_range.

Member functions

(constructor) (C++20)	constructs a lazy_split_view (public member function)
base (C++20)	returns a copy of the underlying (adapted) view (public member function)
begin (C++20)	returns an iterator to the beginning (public member function)
end (C++20)	returns an iterator or a sentinel to the end (public member function)
Inherited from std::ranges::view_interface
empty (C++20)	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>)
cbegin (C++23)	returns a constant iterator to the beginning of the range. (public member function of std::ranges::view_interface<D>)
cend (C++23)	returns a sentinel for the constant iterator of the range. (public member function of std::ranges::view_interface<D>)
operator bool (C++20)	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>)
front (C++20)	returns the first element in the derived view. Provided if it satisfies forward_range. (public member function of std::ranges::view_interface<D>)

Nested classes

outer_iterator (C++20)	the iterator type (exposition-only member class template*)
inner_iterator (C++20)	the iterator type of the inner range (exposition-only member class template*)

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.

Example

Run this code

#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 } { ! }

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

See also

ranges::split_viewviews::split (C++20)	a view over the subranges obtained from splitting another view using a delimiter (class template) (range adaptor object)
ranges::join_viewviews::join (C++20)	a view consisting of the sequence obtained from flattening a view of ranges (class template) (range adaptor object)