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Re: [] Xtext to LPG


As I understand, this does means nothing for the QVTo project. I understand that Ed is trying to obtain LPG grammars from the Xtext one (which are used for the pivot-based implementation's parser, which is not exploited by QVTo, AFAIK). To do that, it looks like he is using a serie of QVTo transformations.

As long as QVTo parser extends the classic OCL LPG grammars (from org.eclipse.ocl.ecore plugin) QVTo project won't have to worry about these activities


El 01/03/2012 16:51, Sergey Boyko escribió:
Hi Ed,

Could you please describe in more details what is "Xtext to LPG" means for QVTo. Could you please point me where QVTo *.xtex is persisted?

About QVTo statndalone execution; look at


On Wed, Feb 29, 2012 at 11:56 AM, Ed Willink <ed@xxxxxxxxxxxxx> wrote:

I made a relatively small Xtext grammar change and suddenly got stupid syntax errors, probably because a magic backtracking precedence flipped. I therefore started updating the 'equivalent' LPG grammar to look for a conflict and realized that the time had come to look at automated Xtext to LPG conversion; it's relatively easy.

I've therefore developed/am developing a Tx cascade
QVTo: *.xtext -> *.xtext.XBNF to get a fully referential EBNF model from the Xtext CST
QVTo: *.xtext.XBNF -> *.xtext.normal.XBNF to convert to a disjunct of conjuncts BNF
QVTo: *.normal.XBNF -> *.inline.XBNF to re-inline non-recursive references that were originally from a single rule
Acceleo: *.inline.XBNF -> *.g, *.gi

(XBNF is Xtext BNF, i.e BNF with model annotations)

Currently plausible KWLexer and Parser grammars are generated, Lexer still todo; the Xtext and LPG styles are very different.

Action code still to do; should be easy with all the model annotations.

Unfortunately there is no QVTo standalone support so I also had to develop that and the corresponding MWE integration.

The build scripts are in the build plugin. The transformations in the examples.xtext2lpg plugin.

Since only the build plugin has QVTo dependencies and neither of the above plugins are in the Tools build, I don';t think that there is any releng impact.


       Ed Willink

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