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

 

C++

Compiler support

Freestanding and hosted

Language

Standard library

Standard library headers

Named requirements

Feature test macros(C++20)

Language support library

Concepts library(C++20)

Diagnostics library

Memory management library

Metaprogramming library(C++11)

General utilities library

Containers library

Iterators library

Ranges library(C++20)

Algorithms library

Strings library

Text processing library

Numerics library

Date and time library

Input/output library

Filesystem library(C++17)

Concurrency support library(C++11)

Execution control library(C++26)

Technical specifications

Symbols index

External libraries

 

Ranges library

Range access begin cbegin   end cend rbegin crbegin   rend crend size ssize   data cdata reserve_hint (C++26)   empty

Range conversions std::from_range_t std::from_range (C++23)(C++23)     to (C++23)

Dangling iterator handling dangling borrowed_iterator_t borrowed_subrange_t

Range primitives
range_size_trange_difference_trange_value_t elements_of (C++23)	iterator_tconst_iterator_tsentinel_tconst_sentinel_t (C++23)(C++23)	range_reference_trange_const_reference_trange_rvalue_reference_trange_common_reference_t (C++23)

Range concepts
range borrowed_range    common_range	sized_range viewable_range    view	input_range output_range forward_range	bidirectional_range    random_access_range contiguous_range	approximately_sized_range (C++26) constant_range (C++23)

Views
view_interface	subrange

Range factories
empty_viewviews::empty	single_viewviews::single	basic_istream_viewviews::istream	iota_viewviews::iota	repeat_viewviews::repeat (C++23)(C++23)

Range adaptors
views::all_tviews::all as_rvalue_viewviews::as_rvalue (C++23)(C++23)   filter_viewviews::filter transform_viewviews::transform take_viewviews::take take_while_viewviews::take_while common_viewviews::common views::counted to_input_viewviews::to_input (C++26)(C++26)	ref_view drop_viewviews::drop drop_while_viewviews::drop_while lazy_split_viewviews::lazy_split split_viewviews::split join_viewviews::join join_with_viewviews::join_with (C++23)(C++23)   concat_viewviews::concat (C++26)(C++26) cache_latest_viewviews::cache_latest (C++26)(C++26)	owning_view 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 closure objects range_adaptor_closure (C++23)

Range adaptor objects

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

lazy_split_view::base

lazy_split_view::begin

lazy_split_view::end

Nested classes

lazy_split_view::outer_iterator

lazy_split_view::outer_iterator::value_type

lazy_split_view::inner_iterator

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     :publicranges::view_interface<lazy_split_view<V, Pattern>>	(1)	(since C++20)
namespace views {     inlineconstexpr/* unspecified */ lazy_split =/* unspecified */; }	(2)	(since C++20)
Call signature
template<ranges::viewable_range R, class Pattern >     requires /* see below */ constexprranges::viewauto 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 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 viewV 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 viewV 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.

Data members

Member	Description
Vbase_(private)	the underlying view (exposition-only member object*)
Patternpattern_(private)	the pattern that is used as a delimiter to split the underlying view (exposition-only member object*)
non-propagating-cache<ranges::iterator_t<V>>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*)

Member functions

(constructor)	constructs a lazy_split_view (public member function)
base	returns a copy of the underlying (adapted) view (public member function)
begin	returns an iterator to the beginning (public member function)
end	returns an iterator or a sentinel to the end (public member function)
Inherited from std::ranges::view_interface
empty	returns whether the derived view is empty, provided only 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	returns whether the derived view is not empty, provided only if ranges::empty is applicable to it (public member function of std::ranges::view_interface<D>)
front	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	the iterator type (exposition-only member class template*)
inner_iterator	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 =[](autoconst& view){// `view` is of std::views::lazy_split_view::__outer_iterator::value_type   for(std::cout<<"{ ";constauto element : view)std::cout<< element <<' ';std::cout<<"} ";};   int main(){constexprstaticauto source ={0, 1, 0, 2, 3, 0, 4, 5, 6, 0, 7, 8, 9};constexprint delimiter{0};constexpr std::ranges::lazy_split_view outer_view{source, delimiter};std::cout<<"splits["<< std::ranges::distance(outer_view)<<"]: ";for(autoconst& inner_view: outer_view) print(inner_view);   constexprstd::string_view hello{"Hello C++ 20 !"};std::cout<<"\n""substrings: "; std::ranges::for_each(hello | std::views::lazy_split(' '), print);   constexprstd::string_view text{"Hello-+-C++-+-20-+-!"};constexprstd::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)