query

A customisation point that queries the value of a property.

constexpr unspecified query = unspecified;

The name query denotes a customization point object. The expression boost::asio::query(E, P) for some subexpressions E and P (with types T = decay_t<decltype(E)> and Prop = decay_t<decltype(P)>) is expression-equivalent to:

If is_applicable_property_v<T, Prop> is not a well-formed constant expression with value true, boost::asio::query(E, P) is ill-formed.
Otherwise, Prop::template static_query_v<T> if the expression Prop::template static_query_v<T> is a well-formed constant expression.
Otherwise, (E).query(P) if the expression (E).query(P) is well-formed.
Otherwise, query(E, P) if the expression query(E, P) is a valid expression with overload resolution performed in a context that does not include the declaration of the query customization point object.
Otherwise, boost::asio::query(E, P) is ill-formed.

Requirements

Header: boost/asio/query.hpp

Convenience header: boost/asio.hpp