Eclipse Community Forums: TMF (Xtext) » Question about Xtext Grammar

Help

Home

Home » Modeling » TMF (Xtext) » Question about Xtext Grammar

Show: Today's Messages :: Show Polls :: Message Navigator

Question about Xtext Grammar [message #556840]

Thu, 02 September 2010 18:59

No real name

Messages: 101
Registered: August 2010

Senior Member

Hi,

Can someone quickly tell me how I can model this scenario in Xtext grammar?

state {
action = ...
condition = ...
condition = ...
}

I have three possibilites: either action or conditions or both should be specified. however it is illegal if neither is specified. Also there can be only ONE action but multiple conditions per state block.

I was thinking of something like this:

(action+=Action)?
((conditions+=Condition)*)?

But this will allow neither to be specified. Otherwise, maybe something like this:

Statements : Type1 | Type2

Type 1:
(actions+=Action)?
(conditions+=Condition)+

Type 2:
(actions+=Action)

Is there a better way to do the above? Thank you for any ideas.

Report message to a moderator

Re: Question about Xtext Grammar [message #556842 is a reply to message #556840]

Thu, 02 September 2010 19:16

Christian Dietrich

Messages: 14665
Registered: July 2009

Senior Member

Hi,

i would take this grammar

State:
	{State} "state" "{"
		action=Action? 
		conditions+=Condition*
	"}"
;

and 'd leave the check to a validator.

or that grammar

State:
	 "state" "{"
		(action=Action | conditions+=Condition) conditions+=Condition*
	"}"
;

~Christian

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

[Updated on: Thu, 02 September 2010 19:26]

Report message to a moderator

Re: Question about Xtext Grammar [message #556843 is a reply to message #556840]

Thu, 02 September 2010 19:12

Ed Willink

Messages: 7655
Registered: July 2009

Senior Member

Hi pg

It's not always a good idea to be pedantically accurate in the grammar.

Your user may not fully understand the rules, so allow the user to type
what the user thinks is sensible and use validation to warn about rule
violation. You may also be able to offer quick fixers/refactoring to
realize what the user has specvified 'illegally'.

Regards

Ed Willink

On 02/09/2010 19:59, pgbackup@yahoo.com wrote:
> Hi,
>
> Can someone quickly tell me how I can model this scenario in Xtext grammar?
>
> state {
> action = ...
> condition = ...
> condition = ...
> }
>
> I have three possibilites: either action or conditions or both should be
> specified. however it is illegal if neither is specified. Also there can
> be only ONE action but multiple conditions per state block.
>
> I was thinking of something like this:
>
> (action+=Action)?
> ((conditions+=Condition)*)?
>
> But this will allow neither to be specified. Otherwise, maybe something
> like this:
>
> Statements : Type1 | Type2
>
> Type 1:
> (actions+=Action)?
> (conditions+=Condition)+
>
> Type 2:
> (actions+=Action)
>
> Is there a better way to do the above? Thank you for any ideas.

Report message to a moderator

Re: Question about Xtext Grammar [message #556849 is a reply to message #556843]

Thu, 02 September 2010 19:32

No real name

Messages: 101
Registered: August 2010

Senior Member

Hi,

Thank you very much for the responses. I now understand about checking the validitity using the validator. I will try it out there.

Kind regards,
pallav

Report message to a moderator

Previous Topic:	how to define grammar for: create package ... end; create package body ... end;
Next Topic:	Refererncing to existing items in Xtext

Goto Forum:

-=] Back to Top [=-

[ Syndicate this forum (XML) ] [

]

Current Time: Fri Apr 19 23:13:40 GMT 2024

.:: Contact :: Home ::.

Breadcrumbs

Sign up to our Newsletter