std::ranges::split_view<V,Pattern>:: begin

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

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

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