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std::ranges::adjacent_transform_view<V,F,N>::begin

constexpr auto begin();
 (1) (since C++23) 
constexpr auto begin() const
    requires ranges::range<const InnerView> &&
        std::regular_invocable<const F&,
            __REPEAT(ranges::range_reference_t<const V>, N)...>;
 (2) (since C++23)

Returns an iterator to the first element of the adjacent_transform_view.

Let inner_ be the underlying ranges::adjacent_view.

1) Equivalent to return /*iterator*/<false>(*this, inner_.begin());.
2) Equivalent to return /*iterator*/<true>(*this, inner_.begin());.

Parameters

(none).

Return value

Iterator to the first element.

Example

A link to test: Compiler Explorer/g++-13.

#include <ranges>
 
int main()
{
    auto sum = [](auto... args) { return (... + args); };
 
    constexpr auto view = std::views::iota(13, 1337)
                        | std::views::adjacent_transform<3>(sum);
 
    static_assert(*view.begin() == 42 and 42 == 13 + 14 + 15);
}

See also

(C++23)
 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)

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