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| Re: Possibility to generate Circular Referenced target model [message #941208 is a reply to message #941147] |
Fri, 12 October 2012 09:46   |
 Ed Willink
Messages: 7655
Registered: July 2009 |
Senior Member |
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Hi
It's certainly possible, but QVTo is only partially declarative so you
need to empathize with its imperative actions.
A circular loop cannot naturally be created in a single regular pass.
Rather than ensuring the referential validity of each loop step and
having a special loop closing step, I recommend what I usually find
necessary in QVTo; code in two passes.
Pass 1 creates the output as a tree, and populates an in2out Dict.
Pass 2 adds cross-references to the tree using the in2out Dict from pass 1.
[If you're clever/lucky you can use 'resolve' in place of the Doct, but
I find resolve hard to understand/debug in practice.]
Regards
Ed Willink
On 12/10/2012 09:45, Alexander Unsonamed wrote:
> Is it possible to somehow handle Circular References?
> My source model has circular references, and I'd like to have circular
> references in generated target model.
>
> E.g.:
>
> result.name := "Model";
> var box: Box := object Box {
> name := "Box node";
> };
>
> var subBox : Box := object Box {
> name := "SubBox";
> };
>
>
> result.root := box;
> box.children += subBox;
> subBox.children += box;
>
>
> So, I have Box with child of type Box. Thus I have possibility to
> create infinite nesting of boxes.
> As a result of transformation, I have result object without any children.
>
> If I remove the following statement:
>
> subBox.children += box;
>
> transformation works well, but I get predefined 1-level nesting.
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| Re: Possibility to generate Circular Referenced target model [message #944881 is a reply to message #944828] |
Mon, 15 October 2012 06:32 |
Ed Willink
Messages: 7655
Registered: July 2009 |
Senior Member |
|
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Hi
Take the simplest of trees with links
A
B, link to C
C, link to B
This can be constructed in containment order
create A
create B
create C
then crossreferenced
assign B link to C
assign C link to B
since when assigning cross references all sources and targets exist.
Cannot be done in one pass.
If A, B, C result from a transformation on a, b, c then in2out Dict contains
a => A
b => B
c => C
Regards
Ed Willink
On 15/10/2012 07:03, Alexander Unsonamed wrote:
> Quote:
>> Pass 1 creates the output as a tree, and populates an in2out Dict.
>> Pass 2 adds cross-references to the tree using the in2out Dict from
>> pass 1.
>
>
> Thanks for the comment, but I really don't understand what you meant
> by in2out Dict. What am I supposed to store in such a dictionary and
> why it cannot be created by one pass?
> Can you supply me with the simplest example, it would be nice.
> Thanks in advance.
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