[over.unary] (original) (raw)
A prefix unary operator functionis a function named operator@for a prefix unary-operator @ ([expr.unary.op]) that is either a non-static member function ([class.mfct]) with no parameters or a non-member function with one parameter.
If a member function is selected, the expression is interpreted as
cast-expression . operator @ ()
Otherwise, if a non-member function is selected, the expression is interpreted as
operator @ ( cast-expression )
[ Note
: The operators ++ and -- ([expr.pre.incr]) are described in [over.inc]. — end note
]