std::ranges::join_view<V>::join_view
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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).
Parameters
| base | - | a view of ranges to be flattened | 
Example
| This section is incomplete Reason: no example |