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A customisation point that applies a concept-preserving property to an object.
constexpr unspecified require = unspecified;
The name require denotes
a customisation point object. The expression asio::require(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:
is_applicable_property_v<T, Prop0> &&
Prop0::is_requirable is not a well-formed
constant expression with value true,
asio::require(E, P0, Pn...)
is ill-formed.
E if N == 0 and the expression Prop0::template static_query_v<T> == Prop0::value() is a well-formed constant expression
with value true.
(E).require(P0) if N
== 0
and the expression (E).require(P0) is a valid expression.
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.
asio::require(asio::require(E, P0), Pn...)
if N >
0 and the expression asio::require(asio::require(E, P0), Pn...)
is a valid expression.
asio::require(E, P0, Pn...)
is ill-formed.
Header: asio/require.hpp
Convenience header: asio.hpp