Re: Access Types

[Tucker Taft <stt@averstar.com>]

Steve Folly wrote:
> ... But what about subprogram
> access type parameters.
> For example, you can have...
> 
>     function Foo(Bar : access Object) return Boolean;
> 
> Which means the function takes an access to an Object variable.
> The function is free to change the value of the variable that Bar 'points'
> to.
> 
> What seems to be missing is something along the lines of...
> 
>     function Foo(Bar : access constant Object) return Boolean;
> 
> Which would imply that the function cannot change the variable the Bar
> points to.
> 
> Why is this not included in the language definition. 

Because it is largely redundant with "Bar : in Object".  If you
don't intend to update the pointed-to object, why not just
pass it "in"?

Be that as it may, I would also like to see "access constant" parameters
added in for orthogonality reasons, and because for certain tagged
types, essentially all of the primitive operations are most appropriately
written using access parameters.  This change will probably be included
in the next round of language enhancements, though there are no guarantees.
I would recommend the use of "in" in the interim.


> ... Is there an
> alternative?

"in"

> 
> --
> Regards,
> Steve Folly -  Y2K compliant since 32nd Februark 1998
> http://www.follysplace.demon.co.uk
> donationsto:myaccount@mybank.co.uk

-- 
-Tucker Taft   stt@averstar.com   http://www.averstar.com/~stt/
Technical Director, Distributed IT Solutions  (www.averstar.com/tools)
AverStar (formerly Intermetrics, Inc.)   Burlington, MA  USA