on the use of "limited with"

on the use of "limited with"

[evangeli]

hello,
i recently downloaded gnat gpl and tested the new Ada 05 feature
"limited with"
here are two packages which defines two types:

limited with q;
package p is
   type tp_record is private;
   type tp is access all tp_record;
   function get_q(my_tp : in tp) return q.tq;
private
   type tp_record is record ... end record;
end p;
--=====================================--
limited with p;
package q is
   type tq_record is private;
   type tq is access all tq_record;
   function get_p(my_tq : in tq) return p.tp;
private
   type tq_record is record ... end record;
end q;

i naturally get the following errors:
p.ads:5:42: invalid use of incomplete type

q.ads:5:42: invalid use of incomplete type

my question is the following: is there a way to declare p and q in two
separate packages?

Re: on the use of "limited with"

[Martin Dowie]

evangeli@cnam.fr wrote:
> hello,
> i recently downloaded gnat gpl and tested the new Ada 05 feature
> "limited with"
> here are two packages which defines two types:
> 
> limited with q;
> package p is
>    type tp_record is private;
>    type tp is access all tp_record;
>    function get_q(my_tp : in tp) return q.tq;

Try
... return access q.tq_record;

> private
>    type tp_record is record ... end record;
> end p;
> --=====================================--
> limited with p;
> package q is
>    type tq_record is private;
>    type tq is access all tq_record;
>    function get_p(my_tq : in tq) return p.tp;

Try
... return access p.tp_record;

Cheers

-- Martin

Re: on the use of "limited with"

[evangeli]

thanks for the help
does not seem to work neither :

function get_q(my_tp : in tp) return access q.tq;
p.ads:5:41: anonymous access type definition not allowed here

do i have to redefine an acces type on q.tq ?

Re: on the use of "limited with"

[Martin Dowie]

evangeli@cnam.fr wrote:
> thanks for the help
> does not seem to work neither :
> 
> function get_q(my_tp : in tp) return access q.tq;
> p.ads:5:41: anonymous access type definition not allowed here
> 
> do i have to redefine an acces type on q.tq ?

Hmmm, from memory, I think after reading John Barnes' paper on this you 
may have to define the access type to the "limited with"-ed type locally 
to where you want to use it.

It may be that all the Ada05 access type/limited with changes are not 
yet implemented either.

Cheers

-- Martin

Re: on the use of "limited with"

[Randy Brukardt]

<evangeli@cnam.fr> wrote in message
news:1128856766.691404.176910@z14g2000cwz.googlegroups.com...
> thanks for the help
> does not seem to work neither :
>
> function get_q(my_tp : in tp) return access q.tq;
> p.ads:5:41: anonymous access type definition not allowed here

Apparently, your version of GNAT doesn't implement this feature yet.

> do i have to redefine an acces type on q.tq ?

Yes, since GNAT apparently doesn't implement anonymous access results. You
are only allowed to use the type directly in subprogram specs. if (1) it's a
tagged type; and (2) it's a parameter (not the return type).

                     Randy.