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[Grammar] Declaration and definition of variables for a DSL [message #555421]

Thu, 26 August 2010 14:31

Michael Frey

Messages: 48
Registered: August 2010

Member

Hi,

I'm working on a DSL where it should be possible to differ between a declaration of a element and the definition of a element. For example:

int a;
int b = 42;
a = 12;

So, I've started with the following construct

VariableDecl:
type=DataType name=ID ';';

whereas DataType refers to my defined data types. I've thought it might be an idea to use cross references like in the following fragment

VariableDef:
name=[VariableDecl] '=' INT;

But that's not working and I doubt that this is the right way. So far, what I really want is to "extend" the already defined element VariableDecl (and Variable might be a better name). I'm new to Xtext and so this question might be quite stupid. Maybe somebody has an idea or can point me into the right direction? Thanks in advance!

Best regards,
Michael

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Re: [Grammar] Declaration and definition of variables for a DSL [message #555441 is a reply to message #555421]

Thu, 26 August 2010 14:45

Alexander Nittka

Messages: 1193
Registered: July 2009

Senior Member

> VariableDef:
> name=[VariableDecl] '=' INT;
should be more like
VariableDef:
ref=[VariableDecl] '=' value=INT;

but otherwise it looks fine to me. Could you be more specific about
*what" is not working?

Alex

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Re: [Grammar] Declaration and definition of variables for a DSL [message #555551 is a reply to message #555441]

Fri, 27 August 2010 07:12

Michael Frey

Messages: 48
Registered: August 2010

Member

Hi,

thanks for the quick reply. Hm, my problem was maybe a problem of general understanding. So far, I've build the following

Variable:
	VariableDeclaration | VariableDefinition;

VariableDeclaration:
	type=DataType name=ID';';

VariableDefinition:
	AlreadyDeclaredVariable | NewVariableDefinition;

AlreadyDeclaredVariable:
	ref=[VariableDeclaration] '=' value=NUMBER ';';

NewVariableDefinition:
	type=DataType name=ID '=' value=NUMBER ';';

But MWE2 in the generator is complaining about

Decision can match input such as "'int' RULE_ID '=' RULE_NUMBER ';'" using multiple alternatives: 1, 2
As a result, alternative(s) 2 were disabled for that input

So the problem might be parsing "int foo = 42" and "int foo"?

Best regards,
Michael

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Re: [Grammar] Declaration and definition of variables for a DSL [message #555560 is a reply to message #555551]

Fri, 27 August 2010 07:35

Christian Dietrich

Messages: 14665
Registered: July 2009

Senior Member

Hi,

i cannot reproduce this since you didn't post your rules for DataType (and number).

Variables: variables+=Variable*;

Variable:
	VariableDeclaration | VariableDefinition;

VariableDeclaration:
	type=ID name=ID';';

VariableDefinition:
	AlreadyDeclaredVariable | NewVariableDefinition;

AlreadyDeclaredVariable:
	ref=[VariableDeclaration] '=' value=INT ';';

NewVariableDefinition:
	type=ID name=ID '=' value=INT ';';

works fine so i think this has to do something with your datatype rule

Regards
Christian

Twitter : @chrdietrich
Blog : https://www.dietrich-it.de

[Updated on: Fri, 27 August 2010 07:36]

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Re: [Grammar] Declaration and definition of variables for a DSL [message #555644 is a reply to message #555560]

Fri, 27 August 2010 13:32

Michael Frey

Messages: 48
Registered: August 2010

Member

Hi,

Quote:

works fine so i think this has to do something with your datatype rule

yepp, you're right. That was the problem!

Thanks,
Michael

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Re: [Grammar] Declaration and definition of variables for a DSL [message #899563 is a reply to message #555644]

Wed, 01 August 2012 13:02

Laigle jérôme

Messages: 26
Registered: August 2012

Junior Member

hi

i have exactly the same problem
what was your problem with your datatype?

what is the solution?

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