std::experimental::ranges::DefaultConstructible
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                    |   Defined in header  <experimental/ranges/concepts>
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|   template< class T > concept bool DefaultConstructible = Constructible<T>;  | 
(ranges TS) | |
The DefaultConstructible concept provides a shorthand for the common case when the question is whether a type can be constructed with no arguments.
See also
|   specifies that a variable of the type can be constructed from or bound to a set of argument types  (concept)  | |
|    checks if a type has a default constructor   (class template)  |