access-to-constant dispatching params

[m_cubed@my-deja.com]

Ada provides access-to-variable dispatching
parameters.

For example:

procedure Set_Exercise_Mode (
  State_Ptr: access State_Type;
  Exercise_Mode: in Exercise_Mode_Type);


What it doesn't seem to provide is
access-to-constant dispatching parameters.
It would be useful to be able to ensure that
a query on an object is prevented from
accidentally updating the object. For example,
(in hypothetical syntax):

function Exercise_Mode (
  State_Ptr: access constant State_Type)
  return Exercise_Mode_Type;


Is there any way of obtaining access-to-constant
dispatching parameters or am I forced to sacrifice
dispatching by using a specific access-to-constant
type:

type RO_Access_State_Type is
  access constant State_Type;

function Exercise_Mode (
  State_Ptr: RO_Access_State_Type)
  return Exercise_Mode_Type;?


Are access-to-constant dispatching parameters
being considered for a future version of Ada?


Sent via Deja.com http://www.deja.com/
Before you buy.