std::ranges::join_view<V>::join_view

std::ranges::join_view<V>::join_view - cppreference.com

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`join_view() requires std::default_initializable<V> = default;`	(1)	(since C++20)
`constexpr explicit join_view( V base );`	(2)	(since C++20)

Constructs a join_view.

1) Default constructor. Value-initializes the underlying view. After construction, base() returns a copy of V().

2) Initializes the underlying view with std::move(base).

base

a view of ranges to be flattened