prefer

A customisation point that attempts to apply a property to an object.

constexpr unspecified prefer = unspecified;

The name prefer denotes a customisation point object. The expression asio::prefer(E, P0, Pn...) for some subexpressions E and P0, and where Pn... represents N subexpressions (where N is 0 or more, and with types T = decay_t<decltype(E)> and Prop0 = decay_t<decltype(P0)>) is expression-equivalent to:

If is_applicable_property_v<T, Prop0> && Prop0::is_preferable is not a well-formed constant expression with value true, asio::prefer(E, P0, Pn...) is ill-formed.
Otherwise, E if N == 0 and the expression Prop0::template static_query_v<T> == Prop0::value() is a well-formed constant expression with value true.
Otherwise, (E).require(P0) if N == 0 and the expression (E).require(P0) is a valid expression.
Otherwise, require(E, P0) if N == 0 and the expression require(E, P0) is a valid expression with overload resolution performed in a context that does not include the declaration of the require customization point object.
Otherwise, (E).prefer(P0) if N == 0 and the expression (E).prefer(P0) is a valid expression.
Otherwise, prefer(E, P0) if N == 0 and the expression prefer(E, P0) is a valid expression with overload resolution performed in a context that does not include the declaration of the prefer customization point object.
Otherwise, E if N == 0.
Otherwise, asio::prefer(asio::prefer(E, P0), Pn...) if N > 0 and the expression asio::prefer(asio::prefer(E, P0), Pn...) is a valid expression.
Otherwise, asio::prefer(E, P0, Pn...) is ill-formed.

Requirements

Header: asio/prefer.hpp

Convenience header: asio.hpp