Re: private properties of tagged records

["Mark Lundquist" <up.yerz@nospam.com>]

"Thomas Nebel" <thomas_nebel@gmx.de> wrote in message
news:9frakn$5qr8r$1@ID-42131.news.dfncis.de...
> Hi
>
> Is there a possibility to make properties of a tagged record "private"?;
> that you can
> access these properties only from a view functions, that have the
exclusive
> "right"
> to access them?
> Otherwise every function could change values in evrey record...
>
> Thomas

It looks like this:

        package Foo is

                type T is private;        -- This means clients of the
package can't see the full type
                                                 -- type definition

                procedure Do_Something (To : T);

        private

                type T is record          -- This is normal record
definition, but it "completes" the private
                    -- whatever...         -- type declaration above
                    --
                end record;

        end Foo;

Now, the full definition of T is visible only in the body of Foo.  So for
instance, procedure Do_Something can access the components of its parameter
To, but some other package that with's Foo cannot access to components of an
object of type T.

Note that:

1) A private type does not have to be a record type, it can be any kind of
type.
2) Ada has no notion of private vs. public components; either the type is
private or it isn't.

Does this help?

Mark Lundquist