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[Acceleo] eInverse() and other functions [message #499713]

Mon, 23 November 2009 14:58

Eclipse User

I'm studying Acceleo, but i cant find documentation about many functions like eInverse, ancestors, siblings.

Does anyone know where i can find documentation about theses functions?

thanks

Andre Silva
Brazil

Re: [Acceleo] eInverse() and other functions [message #499810 is a reply to message #499713]

Tue, 24 November 2009 04:08

Eclipse User

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Hi Andre,

The documentation on non standard services is currently being reviewed
and should be accessible in the next integration build through the
Eclipse help (Help => Help Contents). It is not present at the time of
writing though :'(.

If needed, don't hesitate to post questions here about the services you
need help understanding. For those you posted the names here,

1) "self.eInverse()" returns all elements that reference "self" (inverse
references)
2) "self.ancestors()" returns all ancestors of "self" (tree-wise) : if
package A contains package B which itself contains class C,
"C.ancestors()" will return B and A in this order.
3) "self.siblings()" is once again a tree-wise operation : it will
return all elements standing at the same level as "self" under the same
parent.

Laurent Goubet
Obeo

Andre wrote:
> I'm studying Acceleo, but i cant find documentation about many functions
> like eInverse, ancestors, siblings.
>
> Does anyone know where i can find documentation about theses functions?
>
> thanks
>
> Andre Silva
> Brazil

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Re: [Acceleo] eInverse() and other functions [message #499888 is a reply to message #499810]

Tue, 24 November 2009 08:25

Eclipse User

Hi Laurent

thanks for aswering

i hope this documentation be ready as soon as possible

one more question: how can i obtain the ancestors in reverse order? if package A contains package B which itself contains class C, "C.ancestors()" will return A and B in this order

Andre Silva
Brazil

Re: [Acceleo] eInverse() and other functions [message #499925 is a reply to message #499888]

Tue, 24 November 2009 09:12

Eclipse User

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Andre,

We wanted to add a "reverse()" operation on ordered collection types to
allow just that ... yet such an operation has been planned for the next
version of OCL and thus we decided on not adding a duplicate in.

Till the next version of MDT OCL is out, your only choice to reverse a
list is to create your own 'reverse()' query :

[query reverse(toReverse : Collection(T)) : Sequence(T) =
toReverse->iterate(item; res : Sequence(T) = Sequence{} |
res->prepend(item))/]

Laurent Goubet
Obeo

Andre wrote:
> Hi Laurent
>
> thanks for aswering
>
> i hope this documentation be ready as soon as possible
>
> one more question: how can i obtain the ancestors in reverse order? if
> package A contains package B which itself contains class C,
> "C.ancestors()" will return A and B in this order
>
> Andre Silva
> Brazil

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Re: [Acceleo] eInverse() and other functions [message #500060 is a reply to message #499925]

Tue, 24 November 2009 15:08

Eclipse User

Hi Laurent

Your query really worked!! thanks a lot!

can you answer one more question? is it possible on Acceleo to declare a String variable and manipulate it?

Something like this:
String x = "something";
x.concat("another");

thanks

Re: [Acceleo] eInverse() and other functions [message #500171 is a reply to message #500060]

Wed, 25 November 2009 04:05

Eclipse User

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Hi Andre,

Unfortunately, the MTL specification does not provide a
"generation-free" type of block that would allow to manipulate a
variable without generating the result of this manipulation. You can
declare variables within "init sections" of some blocks (template,
query, for, ... see the specification for details). Manipulating these
variables will always generate the result :

[template test(c : EClass) {x : String = 'something';}]
[x.concat(' another')/]
[x.concat(' once more')/]
[/template]

Will generate the text : "something another\nsomething once more". As a
side note, there is no "affectation operator" in OCL. The "=" operator
is a comparison except in variable initialisation, thus there is no way
to alter the value of a primitve variable beside initialisation.

I raised an OMG issue against the specification for this ... yet
received no word from the MTL task force since then.

Laurent Goubet
Obeo

Andre wrote:
> Hi Laurent
>
> Your query really worked!! thanks a lot!
>
> can you answer one more question? is it possible on Acceleo to declare a
> String variable and manipulate it?
>
> Something like this:
> String x = "something";
> x.concat("another");
>
> thanks

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Re: [Acceleo] eInverse() and other functions [message #500387 is a reply to message #500171]

Wed, 25 November 2009 15:58

Eclipse User

I am not sure that to be able to do something like a = a + b is absolutely necessary.
A behaviour similar to the xslt one would be nice.
You cannot modify a variable but recursive mechanisms allow to do everything you need.
An initialisation part at each block level (not only template) would also be a nice thing...

Re: [Acceleo] eInverse() and other functions [message #500420 is a reply to message #500171]

Wed, 25 November 2009 21:52

Eclipse User

Hi Laurent

Another question: how can i obtain the same result of ancestors() using only standard OCL services? is it too complicated?

thanks

Re: [Acceleo] eInverse() and other functions [message #500469 is a reply to message #500387]

Thu, 26 November 2009 04:52

Eclipse User

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Sebastien,

I am not that familiar with XSLT. Could you elaborate on the behavior
you'd like to see within Acceleo? We are not limited to what the
specification allows us to do; we are free to try and make the
specification evolve. If you see a nice way if providing such
functionalities, don't hesitate to report it to us :).

Laurent Goubet
Obeo

Sebastien Roy wrote:
> I am not sure that to be able to do something like a = a + b is
> absolutely necessary.
> A behaviour similar to the xslt one would be nice.
> You cannot modify a variable but recursive mechanisms allow to do
> everything you need.
> An initialisation part at each block level (not only template) would
> also be a nice thing...

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Re: [Acceleo] eInverse() and other functions [message #500475 is a reply to message #500420]

Thu, 26 November 2009 05:01

Eclipse User

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Hi Andre,

This isn't impossible with pure OCL, we simply decided to provide
simplifications when we thought something would be too cumbersome for
users. In OCL, you can simply make use of the fact everything is an
EObject and use the usual "eContainer()" EOperation, along with some
recursion. That would give something like :

[query public getAncestors(o : OclAny) : Sequence(T) = let container :
EObject = o.oclAsType(ecore::EObject).eContainer() in
Sequence{container}.append(container.getAncestors())/]

Laurent Goubet
Obeo

Andre wrote:
> Hi Laurent
>
> Another question: how can i obtain the same result of ancestors() using
> only standard OCL services? is it too complicated?
>
> thanks
>

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name="laurent_goubet.vcf"
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filename="laurent_goubet.vcf"

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bjoyLjENCmVuZDp2Y2FyZA0KDQo=
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Re: [Acceleo] eInverse() and other functions [message #500508 is a reply to message #500475]

Thu, 26 November 2009 08:17

Eclipse User

Laurent,

Is the 'eContainer()' operation an OCL standard? why can't i see it on OMG OCL documentation and on Acceleo sintax?

thanks

Re: [Acceleo] eInverse() and other functions [message #500529 is a reply to message #500508]

Thu, 26 November 2009 09:34

Eclipse User

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Andre,

eContainer() is an EOperation defined on the ecore metamodel. The query
I gave you here takes advantage of the fact any model modelled through
EMF contains instances of EObjects :). The query won't do the trick,
however, if you decided not to extend "EObject" in the genmodel you used
to generate your metamodel code.

If you haven't used a genmodel, then the model you use for generation is
most likely a ".ecore" model or ".uml" model, the elements of which both
extend EObject.

Laurent Goubet
Obeo

Andre wrote:
> Laurent,
>
> Is the 'eContainer()' operation an OCL standard? why can't i see it on
> OMG OCL documentation and on Acceleo sintax?
>
> thanks

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filename="laurent_goubet.vcf"

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Re: [Acceleo] eInverse() and other functions [message #500585 is a reply to message #499713]

Thu, 26 November 2009 16:28

Eclipse User

Laurent Goubet wrote on Thu, 26 November 2009 04:52

Sebastien,

I am not that familiar with XSLT. Could you elaborate on the behavior
you'd like to see within Acceleo? We are not limited to what the
specification allows us to do; we are free to try and make the
specification evolve. If you see a nice way if providing such
functionalities, don't hesitate to report it to us Smile

.

Laurent Goubet
Obeo

Well, basically, the XSLT and M2T paradygm and goal are quite similar :

They take as input an xml document (specialised for M2T)
They parse this document and transform its elements in text elements as output.
The process is absolutely static : there is no dynamic behaviour : no event, no time. The result of the process only depends on the initial inputs.
You can navigate into the structure of the input document using a specific language : XPath for xslt, ocl for M2T.

The data beeing static, there is no need to dynamic modification of variable.
In xslt, the variable are mainly used as shortcuts. This prevents the developer to have too long or complex expressions and/or copy paste these long and complex expressions in different parts of the code. This is specifically usefull when the variables are used to gather a set of elements that will be used later in the code.
Actually, the variables are not evaluated when they are declared, but when they are used.

example :

<xsl:variable name="foo" select="aVeryComplexExpression($templateParameter1, $currentNode)"/>
<xsl:variable name="result1" select="aTransformation($foo)"/>
<xsl:variable name="result2" select="anotherTransformation($foo)"/>
<xsl:value-of  select="$result1"/>
<xsl:value-of select="$result2"/>

is similar to

<xsl:value-of  select="aTransformation(aVeryComplexExpression($templateParameter1, $currentNode))"/>
<xsl:value-of select="anotherTransformation(aVeryComplexExpression($templateParameter1, $currentNode))"/>

The results are identical but the second expression is harder to write, to read and to maintain when the syntax is a little bit long.

In xslt, you can define variables anywhere in the code. That allow to define variables depending on the current node in a for-each loop, for instance.
(The equivalent in M2T of the "current-node" would be the iteration variable of the "for" loop).

The only drawback of not be able to modify variable is that the computations based on iterations for instance are sometimes more tedious. They have to be performed using recursive algorithms instead.

So, simply allowing to define new variable anywhere in the code would dramatically ease the use of complex expression without breaking the M2T paradigm.

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