Eclipse Community Forums: TMF (Xtext)

Help

Home

Home » Modeling » TMF (Xtext) » Xtext Grammar(Need a variable to have more than one data type)

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

Xtext Grammar [message #1015528]

Fri, 01 March 2013 06:12

rohit ahuja

Messages: 27
Registered: February 2013

Junior Member

Hi All,

I am new to Xtext and writing a DSL.

I have something like

'Case:' CaseName = ID

Now the variable CaseName can contain simple only Integer Values i.e any combination of 0-9, or only Alphabets i.e. any combination of the A-Z or a-z, or a mixed case.
If i keep it as above, xtext doesn't allow me to have a single int value,

say 'Case: 0'

I tried with the below method
'Case:' CaseName = ID|INT -- but it doesn't work for obvious reasons.

If i try to create another terminal like (0-9|a-z|A-Z)*, it starts interfering with other rules in the grammar.

I think there must be some other way, can anyone help me with this?

In general, can any variable be assigned to two types?

Thanks,
Rohit Ahuja

Report message to a moderator

Re: Xtext Grammar [message #1015530 is a reply to message #1015528]

Fri, 01 March 2013 06:48

Christian Dietrich

Messages: 14716
Registered: July 2009

Senior Member

Hi

Did you try a data type rule?

IDORINT: ID|INT;

.... Casename=IDORINT

--
Need training, onsite consulting or any other kind of help for Xtext?
Go visit http://xtext.itemis.com or send a mail to xtext at itemis dot de

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

Report message to a moderator

Re: Xtext Grammar [message #1015561 is a reply to message #1015530]

Fri, 01 March 2013 09:04

rohit ahuja

Messages: 27
Registered: February 2013

Junior Member

Hi Christian,
Thanks for the reply.

If i try creating something like,
terminal IDORINT: ID|INT;

the other places where i have field=ID, starts causing problems, i also get a error message in the console as below,
The token definitions can never be matched because prior tokens match the same input: RULE_ID,RULE_INT

Am i missing something here?

Thanks,
Rohit Ahuja

Report message to a moderator

Re: Xtext Grammar [message #1015564 is a reply to message #1015561]

Fri, 01 March 2013 09:07

Christian Dietrich

Messages: 14716
Registered: July 2009

Senior Member

Hi,

this is a question of lexing and parsing

lexing is done first and is context free.
parsing in done on the lexical token stream and context sensitive.

terminal IDORINT: ID|INT;
is a lexer rule

IDORINT: ID|INT;
is a parser rule (datatype rule)

so use the datatype rule and not the terminal rule

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

Report message to a moderator