std::ranges::cartesian_product_view<First, Vs...>::begin

From cppreference.com
C++
Ranges library
Range adaptors
std::ranges::cartesian_product_view
Member functions
cartesian_product_view::begin
Deduction guides
Iterator
Member functions
Non-member functions
constexpr iterator< false > begin( )
    requires ( ! /*simple-view*/ <First> || ... || ! /*simple-view*/ <Vs> ) ;
(1) (since C++23)
constexpr iterator< true > begin( ) const
    requires ( ranges::range < const First> && ... && ranges::range < const Vs> ) ;
(2) (since C++23)

Returns an iterator to the first element of the cartesian_product_view

Let bases_ be the tuple of underlying views.

1) Equivalent to return /*iterator*/<false>( tuple-transform ( ranges::begin, bases_) ) ;
2) Equivalent to return /*iterator*/<true>( tuple-transform ( ranges::begin, bases_) ) ;

Parameters

(none)

Return value

An iterator to the first element.

Example

Run this code
#include <array>
#include <format>
#include <iostream>
#include <ranges>
#include <string_view>
#include <tuple>
using namespace std::literals;
 
int main()
{
    constexpr auto a = std::array{"Curiously"sv, "Recurring"sv, "Template"sv, "Pattern"sv};
 
    constexpr auto v = std::ranges::cartesian_product_view(a[0], a[1], a[2], a[3]);
 
    constexpr std::tuple<char const&,
                         char const&,
                         char const&,
                         char const&> first{*v.begin()};
 
    std::cout << std::format("{}{}{}{}{}",
                             std::get<0>(first),
                             std::get<1>(first),
                             std::get<2>(first),
                             std::get<3>(first),
                             '\n');
}

Output: 

CRTP

See also

 returns an iterator or a sentinel to the end
(public member function)
(C++20)
 returns an iterator to the beginning of a range
(customization point object)
Retrieved from "https://en.cppreference.com/mwiki/index.php?title=cpp/ranges/cartesian_product_view/begin&oldid=176087