std::default_order

 

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Defined in header <functional>
template< class T > class default_order;		(since C++17)

std::default_order is a type trait that specifies the default strict weak ordering for its type argument T. The associative containers std::map, std::set, std::multimap, std::multiset, as well as the adaptor std::priority_queue uses std::default_order_t<T> by default as their Compare function object.

By default, this trait returns std::less<T>. Users may specialize this trait for user-defined types to provide a different default strict weak ordering.

Member types

Name	Definition
type	std::less<T>; may be specialized for user-defined types.

Helper types

template< class T > using default_order_t = typename default_order<T>::type;		(since C++17)

Notes

std::default_order is intended to be used with types such as std::complex, which have an ordering for their representation, but not for their semantics.

See also

map	collection of key-value pairs, sorted by keys, keys are unique (class template)
multimap	collection of key-value pairs, sorted by keys (class template)
set	collection of unique keys, sorted by keys (class template)
multiset	collection of keys, sorted by keys (class template)
priority_queue	adapts a container to provide priority queue (class template)