NAME¶

std::ranges::split_view::begin - std::ranges::split_view::begin

Synopsis¶

constexpr /*iterator*/ begin(); (since C++20)

Returns an iterator to the first found subrange.

In order to provide the amortized constant time complexity required by the range
concept, this function caches the result within the split_view for use on subsequent
calls. Equivalent to

constexpr /*iterator*/ begin()
{
if (!cached_begin_.has_value())
cached_begin_ = this->find_next(ranges::begin(base_));
return {*this, ranges::begin(base_), cached_begin_.value()};
}

Exposition only data members base_ and cached_begin_ are described here.

Parameters¶

(none)

Return value¶

An iterator.

Complexity¶

Amortized \(\scriptsize \mathcal{O}(1)\)O(1).

Example¶

// Run this code

#include <iomanip>
#include <iostream>
#include <ranges>
#include <string_view>

int main()
{
constexpr std::string_view sentence{"Keep..moving..forward.."};
constexpr std::string_view delim{".."};
std::ranges::split_view words{sentence, delim};

std::cout << "begin(): " << std::quoted(std::string_view{*words.begin()})
<< "\nSubstrings: ";
for (std::string_view word : words)
std::cout << std::quoted(word) << ' ';

std::ranges::split_view letters{sentence, std::string_view{""}};
std::cout << "\nbegin(): " << std::quoted(std::string_view{*letters.begin()})
<< "\nLetters: ";
for (std::string_view letter : letters)
std::cout << letter << ' ';
std::cout << '\n';
}

Output:¶

begin(): "Keep"
Substrings: "Keep" "moving" "forward" ""
begin(): "K"
Letters: K e e p . . m o v i n g . . f o r w a r d . .

See also¶

end returns an iterator or a sentinel to the end
(C++20) (public member function)
begin returns an iterator to the beginning
(C++20) (public member function of std::ranges::lazy_split_view<V,Pattern>)

ranges::begin returns an iterator to the beginning of a range
(C++20) (customization point object)