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Setting rule values implicitly in Xtext Grammar by keyword appereance [message #1786844]

Mon, 14 May 2018 07:56

Alfonso de la Vega

Messages: 13
Registered: January 2016

Junior Member

Hello,

I am developing a SQL-like grammar in Xtext, and I am trying to define the following syntax for attributes of an entity:

   text userId unique;

For that syntax, I created the following rule (not correct, it shows what I want to achieve):

Attribute:
  type=Type name=ID ("unique" {this.isUnique=true})?;

The desired behaviour would be to set an isUnique attribute of the rule to true, just because of the appearance of the "unique" keyword.

Is there a way to define this in the Xtext grammar?

Thank you very much,
Alfonso

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Re: Setting rule values implicitly in Xtext Grammar by keyword appereance [message #1786845 is a reply to message #1786844]

Mon, 14 May 2018 07:59

Karsten Thoms

Messages: 762
Registered: July 2009
Location: Dortmund, Germany

Senior Member

Excerpt from the grammar language manual:
Quote:

The ?= sign (boolean assignment operator) expects a feature of type EBoolean and sets it to true if the right hand side was consumed, independently from the concrete value of the right hand side.

Use as follows:

Attribute:
  type=Type name=ID (unique?="unique")?;

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Re: Setting rule values implicitly in Xtext Grammar by keyword appereance [message #1786846 is a reply to message #1786845]

Mon, 14 May 2018 08:16

Alfonso de la Vega

Messages: 13
Registered: January 2016

Junior Member

Hello Karsten,

You are right, I missed that from the documentation.

Thanks!

Alfonso

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Re: Setting rule values implicitly in Xtext Grammar by keyword appereance [message #1786847 is a reply to message #1786846]

Mon, 14 May 2018 08:20

Karsten Thoms

Messages: 762
Registered: July 2009
Location: Dortmund, Germany

Senior Member

Beyond the documentation it is always useful to look up existing grammars. There are tons of them out there and many have interesting ideas. In the sources from Xtext there are already some good things, or take the Xtext examples that you can install from the File/New menu.

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