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| Visualising an expression grammar [message #1059916] |
Wed, 22 May 2013 07:41  |
 Claudio Heeg
Messages: 75
Registered: April 2013 |
Member |
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Hello.
I have created an Xtext grammar working with arithmetic expressions (and functions and whatnot, but for the sake of this question we'll keep it easy) and now I am wondering whether I could visualise it with just Emfatic annotations and EuGENia.
I'm starting to doubt that, however, but I could be overlooking something terribly simplistic.
The grammar is as follows (as described in [1]):
grammar org.xtext.example.test.Test with org.eclipse.xtext.common.Terminals
import "http://www.eclipse.org/emf/2002/Ecore" as ecore
generate test "http://www.xtext.org/example/test/Test"
Addition returns Expression:
Multiplication ({Addition.left=current} op='+' right=Multiplication)*;
Multiplication returns Expression:
Primary ({Multiplication.left=current} op='*' right=Primary)*;
Primary returns Expression:
NumberLiteral |
'(' Addition ')';
NumberLiteral:
value=INT;
The resulting Emfatic document:
@namespace(uri="http://www.xtext.org/example/test/Test", prefix="test")
package test;
class Expression {
}
class NumberLiteral extends Expression {
attr int value;
}
class Addition extends Expression {
val Expression left;
attr String ~op;
val Expression right;
}
class Multiplication extends Expression {
val Expression left;
attr String ~op;
val Expression right;
}
The general goal is to create a (bidirectially editable) visualisation approximating the AST shown in [1], but any kind of hint could be helpful, especially since this is a rather 'open' question, for lack of a better word.
Thanks for your time.
--
[1] http://blog.efftinge.de/2010/08/parsing-expressions-with-xtext.html
[Updated on: Wed, 22 May 2013 07:42] Report message to a moderator |
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| Re: Visualising an expression grammar [message #1059945 is a reply to message #1059943] |
Wed, 22 May 2013 09:37  |
Claudio Heeg
Messages: 75
Registered: April 2013 |
Member |
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Hello Dimitris,
I actually looked at phantom nodes, i.e. that exact page, a little earlier.
I thought it would only be useful for later finetuning of the model, but it actually seems to have worked decently on first try.
However, the visualisation seems to be missing a level at the top as well as correct names for the operations (see attachment) - that's a mistake in annotations, though, I reckon.
In any case, thanks for your help.
//
After playing around for quite a while, I can say that I have no idea on how to make it work properly, sadly.
Attachment: sample.png
(Size: 9.79KB, Downloaded 232 times)
[Updated on: Wed, 22 May 2013 10:46] Report message to a moderator |
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| Re: Visualising an expression grammar [message #1059971 is a reply to message #1059945] |
Wed, 22 May 2013 12:03 |
Claudio Heeg
Messages: 75
Registered: April 2013 |
Member |
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The following grammar/EMF worked for me. As good as possible.
grammar org.xtext.example.test.Test with org.eclipse.xtext.common.Terminals
generate test "http://www.xtext.org/example/test/Test"
Calcs: calc+=Calculation*;
Calculation:
(literal=StringLiteral operation='=')? term=Addition;
Addition returns Expression:
Multiplication ({Addition.left=current} operation='+' right=Multiplication)*;
Multiplication returns Expression:
Primary ({Multiplication.left=current} operation='*' right=Primary)*;
Primary returns Expression:
NumberLiteral |
'(' Addition ')';
NumberLiteral:
name=INT;
StringLiteral:
name=STRING;
@namespace(uri="http://www.xtext.org/example/test/Test", prefix="test")
package test;
@gmf.diagram(foo="bar",diagram.extension="arith_diagram")
class Calcs {
val Calculation[*] calc;
}
@gmf.node(label="operation")
class Calculation {
@gmf.link()
val StringLiteral literal;
attr String operation;
@gmf.link()
val Expression term;
}
class Expression {
}
@gmf.node(label="name", phantom="true")
class NumberLiteral extends Expression {
attr int name;
}
@gmf.node(label="name", phantom="true")
class StringLiteral {
attr String name;
}
@gmf.node(label="operation", phantom="true")
class Addition extends Expression {
@gmf.link()
val Expression left;
attr String operation;
@gmf.link()
val Expression right;
}
@gmf.node(label="operation", phantom="true")
class Multiplication extends Expression {
@gmf.link()
val Expression left;
attr String operation;
@gmf.link()
val Expression right;
}
However, I run into errors, mostly NPE's, after rewriting formulae.
Example:
to yields an erroneous tree.
After recreating the diagram, those are gone, so I thought I might want to note that in case that behaviour stems from a bug.
Also, on another note: I seem to be unable to reference attributes via the name "~op" (the assignment is "op" in the grammar), even though EMFatic seems to turn them into "~op".
[Updated on: Wed, 22 May 2013 12:28] Report message to a moderator |
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| Re: Visualising an expression grammar [message #1060709 is a reply to message #1059971] |
Tue, 28 May 2013 07:26 |
Claudio Heeg
Messages: 75
Registered: April 2013 |
Member |
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Hello,
after a little work I managed to put up the important formulae in tree-form.
I did this by heavily annotating every function, i.e. every parameter of every function got a gmf.link() to show in the tree.
And that, as you might imagine, caused me to run into out-of-heapspace errors and the like and made it impossible to generate diagram code.
As, first of all, the tree view doesn't look all too nice and secondly is costly, I wonder if I could instead put at lease the Parameters of a proper, non-primitive function (i.e. everything except +-*/) into that function's compartment (or as that function's property)?
I did try gmf.compartment(foo="bar") on the parameters, but that didn't seem to work ("Called feature domainMetaElement on undefined object").
A snippet of the grammar look as following:
Function_Simple:
Abs | Cos;
Abs:
name='Abs''('add=Addition')';
Cos:
name='Cos''('add=Addition')';
As you can see those functions can include additions by themselves, so the corresponding Emfatic file snippet looks as follows:
class Expression {
}
@gmf.node(label="name", phantom="true")
class Function_Simple extends Expression {
attr String name;
@gmf.compartment(foo="bar") // that doesn't work, @gmf.link() does
val Expression add;
}
class Abs extends Function_Simple {
}
class Cos extends Function_Simple {
}
Any help would, as always, be greatly appreciated.
// Edit:
Nevermind, I now transformed that graphic into a pure compartment model. The possibility of an outright mix seems unlikely.
However, putting function parameters into the model as property values still seems interesting.
And, another related question that arose: Instead of modeling the elements as "Abs, Cos, ...", can I just annotate them somehow to only make them "Function_Simple", and, again, have the function's name only as a property value?
It is the same with primitive functions - they'll show up as Addition, Multiplication, ... instead of as an Expression, which makes for poor ability to bidirectionally edit the diagram.
[Updated on: Tue, 28 May 2013 08:19] Report message to a moderator |
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| Re: Visualising an expression grammar [message #1060891 is a reply to message #1060709] |
Tue, 28 May 2013 22:49 |
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Hi Claudio,
It may just be me being too tired after a long day, but I'm afraid I've lost the plot here. It'd really help if you could provide a minimal metamodel and perhaps a sketch of the desired visualisation so that I can investigate.
Cheers,
Dimitris
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