[Seed7-users] Explicit "new" function [was: Dynamic dispatch strange behaviour]

[Thomas M. <tho...@gm...>]

"Leonardo Cecchi" <leo...@gm...> wrote (off-list):
> It works well also for me.
> I don't understand how this explicit "new" function will work: it will
> be used to initialize the interface variable like this?
> 
> const proc: main is func
>   local
>     var strangeInterface: enterprise is new(astronave);
>   begin
>     (* something here *)
>   end func;
> 
> I think it's really useful to visually see when an interface variable
> points to a new value or to an existing implementation value.
> 
> Thanks,
> 
> Leonardo
Yes, it would be used exactly as in your example (maybe without
parentheses). In the moment I use special primitive actions to
create and assign interface variables with an implementation value.
This actions are 'CLS_CREATE2' and 'CLS_CPY2'. This actions accept
interface objects (category CLASSOBJECT) or implementation objects
(everything else, but intended to be of category STRUCTOBJECT).
If the refered implementation object is a temporary expression
it should be made permanent (which I forgot to do in the case
of CLS_CREATE2 - see below for the fix of the bug).

The situation, that implementation objects can point to global or
local objects, which may be constant or variable, and also to
temporary objects (which should be made permanent in the assignment
or create action), is confusing.

As you might guess there is a memory leak in this area.
I plan to use reference counting (or explicit frees when reference
counting is not enough). In that case I have to destinguish between
global and local objects (which need no reference counting) and
managed values (with reference counting).

By the way, here is the fix for the bug you found
(the next version of Seed7 will contain it):
--- /home/tm/old_seed7_5/src/clslib.c 2008-02-10 15:47:51.000000000 +0100
+++ /home/tm/new_seed7_5/src/clslib.c 2008-02-11 13:26:48.000000000 +0100
@@ -175,6 +175,7 @@
       modu_to->value.objvalue = take_reference(modu_from);
     } else {
       modu_to->value.objvalue = modu_from;
+      CLEAR_TEMP_FLAG(modu_from);
     } /* if */
     return(SYS_EMPTY_OBJECT);
   } /* cls_create2 */

BTW.: If possible I would prefer the discussion to be on
see...@li...
That way others can also follow the discussion.

Greetings Thomas Mertes

Seed7 Homepage:  http://seed7.sourceforge.net
Seed7 - The extensible programming language: User defined statements
and operators, abstract data types, templates without special
syntax, OO with interfaces and multiple dispatch.

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