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Keywords available only in specific cases [message #1839965]

Fri, 02 April 2021 10:47

John Henbergs

Messages: 239
Registered: October 2020

Senior Member

Hi all,

I am building the following grammar, where I use inheritance. The user can create a base country or an inherited country by using the keyword "extends". In an inherited country the user can remove trees. However, the keyword "remove" also shows up in a base country, and I want to restrict it, to only be able to remove trees in an inherited country. Is it possible to do that?

Country:
	"country" name=ID ("extends" supercountry=[Country|QualifiedName])?
	forests=Forest
	;
Forest:
	"{" 
	"forest" name=ID "{"
	("tree" trees+=Tree ("," trees+=Tree)*)*
	(("remove") removetree=[Tree])?
	"}";
Tree:
	name=ID
;

Thank you!

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Re: Keywords available only in specific cases [message #1839966 is a reply to message #1839965]

Fri, 02 April 2021 11:08

Neeraj Bhusare

Messages: 177
Registered: July 2009
Location: Canada

Senior Member

You might be able to filter out the proposal by customizing the generated proposal provider class.
If I were you, I would "show an error message" if the user tries to remove the tree from the base.

Twitter : @NeerajBhusare
Blog : https://nbhusare.github.io/
Best regards, Neeraj

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Re: Keywords available only in specific cases [message #1839967 is a reply to message #1839966]

Fri, 02 April 2021 11:18

John Henbergs

Messages: 239
Registered: October 2020

Senior Member

Any idea on how that can be implemented?
An example from some other grammar or something?

Thank you!

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Re: Keywords available only in specific cases [message #1839993 is a reply to message #1839967]

Sat, 03 April 2021 08:22

Neeraj Bhusare

Messages: 177
Registered: July 2009
Location: Canada

Senior Member

Please read the section "Creating Custom Validation Rules" here - https://www.eclipse.org/Xtext/documentation/103_domainmodelnextsteps.html
Please read the validation section here - https://www.eclipse.org/Xtext/documentation/303_runtime_concepts.html#validation
All the Xtext examples that come with Eclipse (File->New->Example...->Xtext Examples) have a validation implementation and I guess some have custom proposal provides too.

Please take some time to study the documentation and the example projects.

Twitter : @NeerajBhusare
Blog : https://nbhusare.github.io/
Best regards, Neeraj

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