[over.call] (original) (raw)
A function call operator functionis a function named operator()that is a non-static member function with an arbitrary number of parameters.
It may have default arguments.
For an expression of the form
postfix-expression ( expression-list )
where the postfix-expression is of class type, the operator function is selected by overload resolution ([over.call.object]).
If a surrogate call function for a conversion function named operator conversion-type-id is selected, the expression is interpreted as
postfix-expression . operator conversion-type-id () ( expression-list )
Otherwise, the expression is interpreted as
postfix-expression . operator () ( expression-list )