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Home » Modeling » TMF (Xtext) » Setting a fixed keyword to start a DSL file (How to set a fixed keyword that would start a DSL file created using Xtext)

Setting a fixed keyword to start a DSL file [message #1799609]

Tue, 11 December 2018 01:19

Eclipse User

Hi,

I am developing a DSL using Xtext as an Eclipse plugin. I need my language to start with a specific fixed expression, e.g: projection FileName ;, where 'projection' is the keyword and 'FileName' is a custom name. Is it possible to do so? I have attached my grammar below. Can anyone kindly tell me how I should change it to achieve my target?

Domainmodel:
	(elements+=MainElement)
;

MainElement:
	ProjectionName | ProjectionComponent | LayerSpecification |
	Description | Capability | Category | ServiceGroup |
	IncludeFragment | {MainElement} Override | {MainElement} Overtake
;

ProjectionName:
	'projection' modelName=ID ';'
;

ProjectionComponent:
	'component' componentName=ID ';'
;

LayerSpecification:
	'layer' layerName=ID ';'
;

Description:
	'description' string=STRING ';'
;

Capability:
	'capability' type=('Online' | 'Offline') ';'
;

Category:
	'category' type=('Integration' | 'ExternalB2B' | 'Users') ';'
;

ServiceGroup:
	'servicegroup' type=('Mobility' | 'Reporting') ';'
;

IncludeFragment:
	('@Dynamic_Component_Dependency' componentName=ID) 'include' 'fragment' fragmentToIncludeName=ID ';'
;

Override:
	'@Override'
;

Overtake:
	'@Overtake'
;

[Updated on: Tue, 11 December 2018 01:20] by Moderator

Re: Setting a fixed keyword to start a DSL file [message #1799610 is a reply to message #1799609]

Tue, 11 December 2018 01:30

Eclipse User

Can you please explain what is not working for you with your grammar

Re: Setting a fixed keyword to start a DSL file [message #1799612 is a reply to message #1799610]

Tue, 11 December 2018 01:44

Eclipse User

Hi

If you need ProjectName first, try putting it first.

Domainmodel:
	elements+=ProjectionName (elements+=MainElement)
;

MainElement:
	ProjectionComponent | LayerSpecification |
	Description | Capability | Category | ServiceGroup |
	IncludeFragment | {MainElement} Override | {MainElement} Overtake
;

Regards

Ed Willink

Re: Setting a fixed keyword to start a DSL file [message #1799614 is a reply to message #1799612]

Tue, 11 December 2018 03:15

Eclipse User

Hi Ed,

Thank you so much for the reply. :) It worked just as you said. In the meanwhile, I too found a bit more complex method which I have mentioned below (The difference between your code and mine is, mine has all compulsory keywords in an order, while yours gives 'projection' keyword first and allows to select any keyword next) : -

Domainmodel:
	(elements+=MainElement)
;

MainElement:
	(ProjectionName rule=ProjectionComponent) rule=LayerSpecification
	(rule=Description) (rule=Capability)? (rule=Category)? (rule=ServiceGroup)?
	(rule=IncludeFragment)* ( Override | Overtake )*
;

However, mine gives both 'layer' and 'projection' keywords at the beginning, which I guess should be corrected using *, ? symbols. So I guess your answer is a better choice.

[Updated on: Tue, 11 December 2018 03:18] by Moderator

Re: Setting a fixed keyword to start a DSL file [message #1799617 is a reply to message #1799614]

Tue, 11 December 2018 03:53

Eclipse User

Hi

The 'better choice' is that one that does what you need flexibly and without errors. You seem to offer a variety of alternatives that don't do what you want and certainly have errors such as multiple assignment to rule. I suggest you revisit some tutorials so that you understand the capabilities that Xtext offers you.

Regards

Ed Willink

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