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std::ranges...view::begin(3)   C++ Standard Libary  std::ranges...view::begin(3)

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.be-
     gin()})
		    << "\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{*let-
     ters.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)

http://cppreference.com 	   2024.06.10	    std::ranges...view::begin(3)
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