Description

Defines a free/non-member operator overload for unary operator op_name that produces an expression instantiated from the expr_template expression template.

The parameter to the defined operator overload may be any type that is not an expression and for which

udt_trait<std::remove_cv_t<std::remove_reference_t<T>>>::value 

is true. The parameter is wrapped in a terminal expression.

Example:

template <boost::yap::expr_kind Kind, typename Tuple>
struct user_expr
{
    static const boost::yap::expr_kind kind = Kind;

    Tuple elements;
};

template <typename T>
struct is_vector : std::false_type {};

template <typename T, typename A>
struct is_vector<std::vector<T, A>> : std::true_type {};

// Defines an overload of operator!() that applies to vectors and returns
// expressions instantiated from user_expr.
BOOST_YAP_USER_UDT_UNARY_OPERATOR(logical_not, ::user_expr, is_vector)