Subject: Re: Generic formal access types
Date: Fri, 02 May 2003 11:52:05 +0200
Date: 2003-05-02T11:52:05+02:00 [thread overview]
Message-ID: <3eb23fca$1@epflnews.epfl.ch> (raw)
In-Reply-To: 5Ejsa.170717$gK.261651@rwcrnsc52.ops.asp.att.net
tmoran@acm.org wrote:
>>Ok, it is not very useful to have an access type if you do not know its
>>content, but the package implements a list and I am just storing them. I
>>"need" that because I want to return the value "null" from a function in
>>the generic package that returns "Access_Type".
>
> What's wrong with
> generic
> type Element is (<>);
First of all, I wrote this too fast and it is erroneous. It should read:
generic
type Element (<>) is private;
> package Lists is
> type Node_Content_Ptr is access Element;
If I declare the access type in the package, I will have a problem with
the return type of the function:
function Whatever return Node_Content_Ptr;
Because I already have access types defined where I do the instantiation.
declare
type Ptr is access Integer;
package Instance is new Generic_Package (Integer);
P : Ptr;
begin
P := Instance.Whatever;
end;
Here, P is of type "Ptr" and the function returns "Node_Content_Ptr".
For the compiler to accept this, I will have to declare Ptr as "access
all Integer" and do an explicit conversion:
P := Ptr (Instance.Whatever);
Since I cannot change the definition of Ptr, this solution is not valid
for me... Nice try, though! :^)
Rodrigo
next prev parent reply other threads:[~2003-05-02 9:52 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-04-30 18:30 Generic formal access types
2003-04-30 19:27 ` Simon Wright
2003-05-01 8:58 `
2003-04-30 21:42 ` Chad R. Meiners
2003-05-01 9:06 `
2003-05-01 9:58 ` Martin Krischik
2003-05-01 13:00 `
2003-05-02 9:14 ` Ludovic Brenta
2003-05-02 10:43 `
2003-05-02 10:50 `
2003-05-01 10:09 `
2003-05-02 1:14 ` tmoran
2003-05-02 9:52 ` [this message]
2003-05-02 16:18 ` tmoran
2003-05-02 16:57 ` Robert A Duff
2003-05-02 19:39 ` Randy Brukardt
2003-05-05 8:14 `
2003-05-05 16:40 ` Matthew Heaney
2003-05-05 17:34 ` Robert A Duff
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